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fine KEVATIONZOF PLANTS TO 
SLD BEV ES 


A STUDY OF FACTORS AFFECTING THE 
DISTRIBUTION OF MARINE PLANTS 


BY 
DUNCAN S. JOHNSON AND HARLAN H. YORK 





WASHINGTON, D. C. 
PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON 
1915 


CARNEGIE INSTITUTION OF WASHINGTON 
PUBLICATION No. 206 


Copies of this Gor 
were first issued 


DEC 311915 


The Lord Baltimore Press 


BALTIMORE, MD., U. 8. A. 


x 


I. 
II. 


III. 


IV. 


‘a 
XN 
+ ¥, 
‘a Maes 
VIL. 
> VIII. 


are IM 
NW. CONTENTS. 


Initiation of the Work; Its Purpose; Acknowledgments................ 
Location and Physical Features of the Area Studied; Mode of Deter- 
mining and Mapping the Distribution of Plants, Physiog- 

EN IUCR Ua ek LS cain Fah anne VS os RAG aso dla Wid Bean dw © ahs 

1. Location, Construction of Map, Mode of Discovering and Recording 
thie: Postlionss of4 Planter: 4 4.6r oir. Cee ee ces ecees 

2. Topography of Harbor; Size, Depth, Character of Bottom and Shores. 
3. Tide-levels; Mode of Determining Height and Rate of Rise and Fall 
CE OS ee ee eM ee eee re hes Cee Re ae CL Ee RS ate mae tree eae 

Plant Associations; Characterization of the Belts or Zones of Vegeta- 
tioneana. Their. DIStripntion. 0. co. cee st he eee ec ey wee ease 

LON A: PUREST LUBE CLL rere cee le GME Snares MONS eae ere ete ere eo ee oe ee sc sée ea 
2. The Bottom Vegetation of the Harbor from —5 to +41.5 feet (the 
Sub Littoral and Lower Littoral Belts).................. 

A. Plants of Loose Soil (The “ Enhalid Formation ” of Warming).. 

B. Attached Alge of Harbor Bottom: ‘“ Lithophilous Benthos’”’.... 
COEpiphytic Atere on Sostora-and) Ulver. Pe. Clee. Oe cw icees 
"The Midtittoralshelt tron £6 to 0 Teer. Fe Sr eS SO oe ca ae 
Ai Tite MiG-Hiiioral Marsico ee ee ete oe eh ce wakee bases ene 

Per RiuGtSPArlLind Petal AOSOCIALIOM Sie ce kek wa ee d's a See eae kas 

oo bie Ale OL the MiIG-ttOral Marah ss oo... oe ues ww coe ow 

B. The Mid-littoral Rockweed Association, on Wharves........... 
Poet i OCE LaALLLOreti. Get, 1 TONG. LO. LOCK 6 oo. ac aa5 pices 6 accsoisile ) wave 2 ol 
A. Seed Plants of the Upper Littoral Belt (Associations of Spar- 
tina patens, Sueda, Salicornia, Juncus, or Scirpus)....... 

Pee ae OF Le CCE LLLOLAT TIGA, fat tins gs a cutaeus t svlekre age ath « vs se « 

ee ire tee COPaL Et CATO G00 he COOL oc ccte scan « 5 cas steuuheeo Le cuake widiain 
A. The Supra-littoral Beach or Storm Beach.................... 

1. Storm Beach of the Spit (from 8 to 12 feet)............... 

2. The Supra-littoral Beach, or Storm Beach, of East and West 

Sides of the Harbor (from 8 to 10 feet).................. 

B. Supra-littoral Belt of the Marsh, or Brackish Marsh (8 to 10 ft.). 

6. Description and Map of Belt Transect of the Marsh (1.5 to 10 ft.).... 
Factors Influencing the Distribution of Littoral Plants................ 
ss EE Pe eee ee aa a Ree etre ene as on eae eee ane, sean 
A. Living Substrata (Plante or Animals) oc... ce he ee we hes 

Peep OT Divi iret at cee ee ee ue deus ee tsees a tie ces fo Lite oo ens tie 

1. Soils as Substrata (Gravel, Sand, Mud, Humus, or Peat).... 

2. Solid Substrata (Stones, Pebbles, Shells, Piles, and Logs)... 

Zn (HNMEUCE OL TW ALEr-CUlTeCn tints ce ate ae ee ee eee each eee 
3. Character of Tidal Changes and their Influence on Plant Distribution. 
Uonracter and Mabnitugae OF, LNG. T1GCH oc 2c i. esc ce 2 esse cette. 
. Effect of Tidal Changes in Water-level on Evaporation or Trans- 
Piva ciOl LEO. CUS Piatti ys ay a cae <e Steced ote aharate Ole ie 

es suilect, Of “Lidal Changes on Aeration. 3.265 30. 5.. bosses eke ws cue 
. Effect of Tidal Changes on Salinity of Soil Water at Higher 
PE VELE Pee ce eae a we ee ere che are eo aid eee eee 

. Effect of Tidal Changes in Exposing Plants to Rain............ 
. Effect of Tidal Changes on the Light Supply Reaching Plants... 
4 “The sannicy oO. the Water of the Harborise . oe cow cscs veces 
bola ne “lentperatiure Of the Water oe ber lis vars es. cate thc poe ecco. v0 Sian 
rae yeast CI OLS ets eae Oi votes tee ce Cae habe cree ein mite 
List of Vascular Plants of Bottom and Shore, with Vertical Range, and 
Physical Characteristics of Habitat of Hach.............. 

List of Thallophytes Occurring Below the 10-foot Level................ 
SETAE ULO LI COLOriet ii ncn ein: ocr spruce « Te one Ge he Ore eee ie aes 


INDEX OF TABLES. 


oo 


weld 


ya oa 


© TABLE A. Duration of daily submergence and exposure of soil at various tide- 


% 
; 
‘Oh 


Be eke RR RP bate Lg cg et bole ale gears ator dy Se a, he A eat oe 
Number of submergences per month and for growing season of 
HISREr MAG-lavelas cee eee ee i Oe ee SASL SS 
Number of exposures per month and for the growing season of 
fower! Cide-1evele \ 5s ete ee es Re ey ame al. Se eh Ame ee UN Gok 
Daily exposure of various tide-levels to daylight.................. 
Vertical distribution of commoner plants in the vegetational belts 
List of vascular plants, with analysis of the habitat of each........ 
List of thallophytes, with the habitat of each species.............. 


oD tee 2 p= ry x, = 


£ mi 2) i 
eve cera + 


wh 


anno O 


Page. 


LIST OF ILLUSTRATIONS. 


Facing page. 
8 


PLaTE I. Map of Inner Harbor at Cold Spring Harbor, showing topography 
II. A. View over Harbor Bottom at Low Water, showing Ulva and the 
Tide-channels from Creek. B. Looking over Harbor Bottom 
toward northeast, showing Ulva, Tide-channels from Tide Pond, 
and Spartina: G1@bri es siaiscis'n\s dnthe Slats nie aeons om DATED ahd e's «)k 
III. A. Spartina glabra and Fucus vesiculosus spiralis on Spit. B. Wall 
of Wharf on the East Shore, showing Fucus and Ascophyllum.... 
Iv. A. South Shore of Spit, showing Upper Margin of Spartina glabra, 
also Sueda, Ammophila, Solidago, and Ailanthus. B. Portion of 
East Shore south of Mill, with Spartina glabra, Scirpus ameri- 
canus, Sambucus, Ailanthus, Solidago, and Iris.........cececvee 
V. Map of Spit, showing Distribution of Seed Plants (1: 1000)........ 

[In above plate Hlymus virginicus should read Huphorbia polygonifolia.] 
VI. Chart of Tide-curve observed at Cold Spring Harbor, July 11, 1911.. 
VII. A. South Shore of Spit, showing cross-section of Belt of Spartina 
glabra left by mowing. B. South Shore of Spit, showing Zonation 
between the 6-foot and 10-foot levels... ...... cc cee cee eee ee eee 
VIII. Map showing the Distribution of important Schizophycee, Diatomee, 
and Chlorophycesr in the Inner Harbor.............cccccececces 
IX. Map showing Distribution of important Phzeophycee and Rhodo- 
DHYCEB IN ANNES. PACD oie nisl y alata oes Gaede cementite iaia ao «tees 
X. South Shore of Spit at 7-foot level, showing Limonium, Sueda, 
Salicornia, ete. B. South Shore of Spit with Salicornia ambigua, 
LAMONIN [and caleal Tels is. cca s acpebs is eis Ain He clone e < sb 
XI. Map showing Distribution of Cormophytes on the Atstuarial Marsh. 
XII. Map showing Distribution of the Vascular Plants of the Inner 
Harbor that are Associated with Fresh-water Inlets............. 
XIII. Map showing the Distribution of Vascular Plants of Inner Harbor 
not Associated with Fresh-water Inlets..............ceeeecees 
XIV. Belt Transect of Spit, showing Distribution of Vascular Plants in 
Relation: tos TIGSLOVGlS sinc cts «acs ie, cla yiesatew veep ears Mites ete xe cela cee 
XV. A. View over Marsh from Causeway at High Tide. B. View over 
Creek and Marsh at Low Tide....... 5-4, a.9'5'a i inl aca en aches 
XVI. A. Fucus vesiculosus var. spiralis. B. An Attenuate variety of 
Fucus vesiculosus from, Mud Plats «o4 sic ses hele spats dnis a ciate 6 Ae se 0 
XVII. Wall of Wharf on West Side of Harbor, showing Zone of Fucus and 
ASCODRYTMUMN sacs os « pcthesd suiarGa bi wibie a eal clehsiins oh eens tia saa eee ee 
XVIII. A. Wall of Wharf and Pebble Bottom along East Shore, showing Dis- 
tribution of Ascophyllum and Fucus. B. Sporelings and Mature 
Plant..of, FUCUSs: CVGNCECONS 6 a aie auis we cis dere Kuen Spats ein skkulss nals s < 
XIX. A. View looking from Causeway Northwest over Marsh. B. View 
of Marsh, showing Line of Contact of Scirpus americanus and 
SParlinGd DGECNS sons gales a oe pha ealyl< dutk shee sipheneKe ania ie oan aan as 
XX. A. View of Marsh, showing Spartina glabra, S. patens, Juncus 
Gerardi, and Scirpus americanus. B. View of South Shore of Spit 
at the 8-foot level, showing Spartina glabra, S. patens, Distichlis, 
Solidago,’ BNG SWAG. s. io oe: easels, av <ikee ok amines atk aota cit psi Ae oe male 
XXI. Belt Transect of Astuarial Marsh (Sections I and II)............. 
XXII. Belt Transect of Astuarial Marsh (Sections III and IV).......... 
XXIII. Predicted Tide-Curve for Willet’s Point, for May 1 to 5,1911....... 
XXIV. Chart showing Range of:Tides at Cold Spring Harbor for Growing 
season, May to Oct JST. vs e258 on eee Lee eee ee a he ee ee ae 

TEXT FIGURES. 

Fig. 1. Vertical North and South Section of Spit........ Re RIS cM te 6 ays 
2. Zonation of Vegetation on South Beach of Spit .................02. 
3. North and South Section of Marsh and its Vegetation................ 
4. Chart‘of -Tides-atWillet's, Pointua tm Ae ee iten es a eh cc 
5. Atmometer used between Tide Lines............... SE PO OA a 


4 


16 
36 


THE RELATION OF PLANTS TO TIDE-LEVELS. 


A STUDY OF FACTORS AFFECTING THE DISTRIBUTION OF MARINE PLANTS 
AT COLD SPRING HARBOR, LONG ISLAND, NEW YORK. 


By Duncan S. JOHNSON AND HARLAN H. YorK.! 


I. INITIATION OF THE WORK; ITS PURPOSE; 
ACKNOWLEDGMENTS. 


The present studies were begun, in the summer of 1905, by Duncan S. Johnson 
and Mary Lentz Johnson, at the Biological Laboratory of the Brooklyn Institute 
of Arts and Sciences, at Cold Spring Harbor, New York. They have been 
continued during the summers of 1906 to 1913 by the authors. 

During the progress of the work, which sometimes demanded the cooperation 
of several men working at once, other members of the Laboratory have aided us, 
among them Messrs. W. H. Brown, G. C. Fisher, W. E. Maneval, and L. H. 
Sharp. Thanks are due especially to Dr. C. B. Davenport, Director of the 
Laboratory, who afforded facilities for carrying on the work and gave suggestions 
concerning the construction of the maps. Professor Francis E. Daniels, of St. 
Johns College, Maryland, rendered valuable aid in making tide records and in 
surveying parts of the harbor. We have also to thank Professor H.S. Conard, of 
Grinnell College, Iowa, for contributing an important section of the descriptive 
portion of this paper. In the summer of 1909 Professor Conard, with the aid 
of Mr. Paul M. Collins, plotted in minute detail the distribution of the vascular 
plants of a carefully selected area on the Spit and one on the Marsh. The 
- results are given in plates XIv, XxI, and xx11, and in the explanations of these 
on pages 113 to 121. In the summer of 1910 Miss Stella G. Streeter, of Jersey 
City, made a study of the rate of growth of certain Ulvacese, Fucacee, and 
Rhodophycee, of the salinity of the water in several tributaries of the harbor, 
and of the soil-water at several points on the Marsh. Her results are embodied 
in Sections III and IV. Dr. A. F. Blakeslee secured specimens of alge for us 
in the winter of 1912-13. To Mr. F. 8. Collins, of Malden, Massachusetts, 
and Dr. Albert Mann, of Washington, D. C., we are under obligation for the 
identification of various alge and diatoms. 

These studies have been confined chiefly to the small “ Inner Harbor,” on 
which the Biological Laboratory is located. The field work has been done by 
both authors in the time they could spare from their work of instruction in this 
Laboratory, during July and August of the years mentioned. Visits have also 
been made to the harbor in April, in June, in late September, and at the end of 
November, for the sake of comparing the condition of the vegetation at these 
times with that found in midsummer. This paper has been written by the 
senior author, except the chapters attributed to others, below their titles. 


1 Botanical contribution from The Johns Hopkins University No. 42. 


6 THE RELATION OF PLANTS TO TIDE-LEVELS 


The purpose of these studies has been to determine and record the distribution 
of the plants occurring in this harbor in relation to external conditions. The 
external factors considered are: topography, substratum (including subsoil), 
and salinity of soil-water; the time of submergence and exposure due to tides ; 
water-currents and the effect of immersion in fresh water during low tide. An 
attempt has been made to determine, as far as is possible from direct observation, 
which of the various external factors are the effective ones in determining the 
distribution of each plant or plant society. 

It is believed that such a record of the present distribution of the plants of this 
harbor, in relation to external conditions, will be of value in several ways. In 
the first place, the vegetation in question will serve as a type for many of the 
harbors on the north side of Long Island and on other parts of our coast. 
Secondly, the relative importance of the various factors affecting the distribution 
of marine plants in general may be perceived in part from a consideration of the 
conditions here described. Thirdly, it is also true that a comparison of the 
conditions and the plant distribution existing in this area two or three decades 
hence with those here recorded should indicate to what changes in conditions 
any changes in the distribution may be due. Such a comparison will certainly 
aid in giving a clearer conception of the causes of plant succession among littoral 
associations. Fourthly, in this general study of the factors affecting the 
distribution of these plants, the particular problems likely to yield valuable 
returns for experimental study have become more clearly defined. It is well 
understood, of course, that most of the problems of distribution here dealt with 
can not be adequately solved till the physical conditions of the environment are 
accurately measured. 


II. LOCATION AND PHYSICAL FEATURES OF THE AREA 
STUDIED. MODE OF DETERMINING AND MAPPING 
THE DISTRIBUTION OF PLANTS, THE PHYSIOG- 
RAPHY, AND TIDE-LEVELS. 


1. LOCATION, CONSTRUCTION OF MAP, MODE OF DISCOVERING AND 
RECORDING THE POSITIONS OF PLANTS. 

Cold Spring Harbor is on the north side of Long Island, 30 miles east of New 
York City. The Inner Harbor, with which we are concerned here, opens by a 
narrow channel from its northeast corner into the Outer Harbor. The two 
harbors are separated from each other by a spit of sand and gravel, locally 
known as the “ Spit ” or “ Sand Spit,’ the former of which names we shall use 
for this barrier. The Outer Harbor opens into Long Island Sound 5 miles north 
of this Spit. The studies here recorded have been confined chiefly to the Inner 
Harbor, which, because of its size, its relatively quiet water, and its proximity 
to the Laboratory has proven a very satisfactory area for study. 

The map of the harbor here used (plate 1) has been built up from an enlarge- 
ment of a map prepared in 1901 by H. R. Codwise. In the course of our work a 
series of contours, above and below the water-level, and many details in the 
topography, wharf-lines, etc., have been added to the original enlargement. 

As a means of accurately locating points of importance for the topography 
of the harbor, or in plant distribution, several lines of range-stakes were driven 
in the bottom and on the shores. The main north-and-south axis in our map 
is along a line running due north for 2,800 feet from a large pile at the 
southwest corner of the Inner Harbor. ‘This pile is about 3 feet to the 
shoreward of the wharf-line and 90 feet south and east of the nearest corner of 
_ the Biological Laboratory. Stakes were driven in the bottom of the harbor at 
intervals of 200 feet along the length of this line. Eastward from the same 
pile a second line of stakes, also 200 feet apart, ran over the bottom of the 
harbor and then across the north end of the estuarial marsh south of the 
harbor. ‘These main north-and-south and east-and-west axes were laid out by 
a small surveyor’s compass. When tested later by a professional surveyor their 
directions were found to be correct within a few minutes of arc. The distance 
between stakes was measured with a considerable degree of accuracy, by means 
of a steel tape or a piece of steel wire exactly 200 feet long. This was a 
somewhat difficult proceeding, since nearly all the measuring on the north-and- 
south axis had to be done from boats. But by hooking a loop at one end of the 
wire over a nail in the center of the last stake set, and then placing the center 
of the other stake exactly at the other end of the wire, a considerable degree of 
accuracy was attained. The total distances measured correspond closely with 
those indicated by Codwise and those on the United States topographic map. 

All distances mentioned in this paper, in noting the position of plant-groups 
or contours, are in feet, since this is the unit used in the United States 
topographic map and in the tide-tables published by the Coast and Geodetic 


7 


8 THE RELATION OF PLANTS TO TIDE-LEVELS 


Survey. Since, however, the scale of the map (plate 1) is 1: 4,000, the metric 
value of any horizontal distance may readily be obtained by applying a metric 
scale directly to the map. 

After the stakes along the two main axes were in place, stakes were set along 
the east and west sides of the harbor and over the Marsh and Spit to serve as 
range-stakes. The stakes along the sides of the harbor were set due east and 
west of the stakes of the north and south axis, by means of a mariner’s quadrant. 
This is the only instrument that can be satisfactorily used in a floating boat. 
Stakes were placed by the aid of the same instrument, at 200 feet and 400 
feet south and 200 feet north of each stake in the main east-and-west axis 
across the Marsh. A line of stakes at 200-foot intervals by measurement 
was run westward on the Sand-spit from the stake in the main north-and-south 
axis, at 2,600 feet north. Range-stakes were then set at 400 feet south of each 
of these. A similar line was run eastward from the stake at 2,800 feet north in 
the north-and-south axis. A range-stake was then placed 200 feet south of each 
of these. 

When all these stakes were in place, by sighting with the aid of a field-glass 
one could determine the position of points in the harbor which were in range 
with any two stakes in the same north-and-south line, or of any two in the same 
east-and-west line. By measuring perpendicularly to these range-lines with a 
tape, the position of any point about the harbor with reference to any range-line, 
and so with reference to the main north-and-south and east-and-west axes, could 
be determined. By the intersection of the range-lines passing through the 
stakes of the longitudinal series with lines passing through the stakes of the 
transverse series, the harbor was divided off like a checker-board into squares, 
each square being 200 feet on a side. This is shown clearly on the map, where 
there is indicated by an xX each intersection which was actually marked by a 
stake in the harbor, on the shore, the Marsh, or the Sand-spit. 

_ ‘The first work to be done after the harbor had been staked off was to correct 

in detail the outline of the harbor, with its surrounding beaches, marshes, and 
wharves. The heavy solid-black boundary line, shown on the map, indicates the 
8-foot tide-line, wherever the harbor is bordered by the natural sloping beach 
or marsh. The portion of the shore-line bordered by the vertical walls of stone 
wharves, which vary in height from 7 to 9 feet, is indicated by the addition of 
short transverse lines to the heavy line of the 8-foot level. The exact outline of 
the shore on the east and west sides of the harbor was determined by measuring 
with a tape on each transverse range-line the distance of the shore-line east or 
west of the nearest north-and-south range-line, and so, practically, the distance 
east or west of the main north-and-south axis. Where the shore line is irregular 
measurements were made at several points between the successive east-and-west 
range-lines. The points so determined were plotted in on the map. With this 
map in hand in the field a line was drawn connecting these points and showing, 
as accurately as possible, the minor irregularities of the shore-line between the 
measured points. 

The method of marking the shore-line on beach and marsh, when the water 
was at the 8-foot level, was the same that was used for determining and marking 
other tide-levels, and will be described below. 

The locations of plants or the boundaries of plant groups growing on shore 
or on accessible parts of the harbor bottom were usually measured by rod or 





~~ 


JOHNSON AND YORK. 





\ : 










JOHNSON AND YORK. 































































































Scale 1:4000 








0 100 =. 200 300 400 SOOFEET 
[he Se ee ee 
ELEVATIONS AND DEPTHS IN FEET 


~~ — Tide lines (even feet) 


2005, [------] Tide lines (odd feet) 


fromm] Whar line 
Location of range stake 
400 















STATION FOR 
EX PERIMENTA 
EVOLUTION 







nA] Lower limit of Spartina glabra 
ror p Limits of Zostera marina 





6006 


| 


1000 W. 800 600 400 200 W. 0 LOOK 400 1000 1200 400 E. 





Map oF INNER Hargor, Corp Spring Harpor, Lona Istanp, NEw York. 


By Duncan 8S. Jonnson and Hartan H. York, 


TOPOGRAPHY OF THE HARBOR 9 


tape in the manner noted for measuring the boundary of the harbor. When the 
position of plants or tide-limits had to be determined in parts of the harbor 
where, because of water or a muddy bottom, the rod or tape could not be used, 
it was necessary to estimate distances within each 200-foot square. This was 
done by setting temporary stakes at the nearest points in the nearest north-and- 
south, and east-and-west range-lines, and then, after rowing away from these to 
the point to be located, estimating the distance in boat-lengths, and converting 
it into feet. The accuracy of the estimate made was considerably increased by 
making duplicate estimates, usually from range-lines on opposite sides of the 
point to be determined. The error still present in any of these estimates is 
small in proportion to the magnitude of the distances measured. 

The procedure in determining the outlines of the areas occupied by Zostera 
marina may serve as an example of the mode of measuring distances within 
each 200-foot square. Starting from one end of the harbor, on a quiet day, 
with half tide and clear water, the boat was kept along one longitudinal 
range-line from end to end of the harbor. The points at which Zostera was 
first encountered (in a density of 10 or more shoots per square yard), at the 
south end of the harbor, and the points at which it disappeared at the north 
end, were noted. The distances of these from the nearest east-and-west range- 
line, and so from the zero-point, were then estimated. After each longitudinal 
range-line had been followed in this way, the boat was rowed along each 
transverse range-line, and the distance east or west of zero of its intersection 
with the boundary of the Zostera was noted. Connecting up the two series of 
points thus located tended to reduce considerably the error that might occur if 
the intersection of the Zostera boundary with one series of range-lines only 
had been determined. 


2. TOPOGRAPHY OF THE HARBOR; ITS SIZE, DEPTH, CHARACTER OF 
BOTTOM AND SHORES. 

The deep, narrow valley occupied by Cold Spring Harbor has been cut out 
from the mass of gravelly morainal deposit, which makes up this part of Long 
Island, chiefly by one considerable fresh-water stream. The elevation of this 
terminal moraine along the sides of the harbor is 50 to 225 feet above sea-level. 
The nearly flat bottom of that part of the valley in which the Inner Harbor 
lies is just covered at high water, while more than half of it is left bare at low 
water. 

- The upper, or south, end of the valley is occupied by a fresh-water stream, with 
a flow of something over 100 cubic feet per minute. ‘’his main stream, which 
we shall speak of as the “ Creek,” enters the harbor through a culvert under the 
highway, at 580 south by 820 east. A second smaller stream, largely of artesian 
water, coming from the pools of the New York State Fish Hatchery, enters the 
harbor from under the same highway, at a point 100 feet west of the main 
stream or Creek. A third stream, also small, is fed chiefly by springs 200 feet 
or so south of the highway, and it enters the harbor about 70 feet east of the 
creek. 

Beginning at a point about 350 feet above the previously mentioned culvert, 
the main stream is dammed at three points to form large ponds. Each of 
these ponds is bordered, especially at the southern or upper end, by a densely 


10 THE RELATION OF PLANTS TO TIDE-LEVELS 


wooded swamp. From the lateral banks, especially the western, the ponds are 
fed by numerous rivulets of cold spring-water, all of them first coming to the 
surface within a few yards of the margin of the pond. 

The Inner Harbor, as shown on the map (plate 1) is, at high water, about 
3,500 feet long. It has a width of about 400 feet near the south end, and 
widens to an extreme width of 2,200 feet at the north end. The total area of 
the water-surface at the 8-foot tide-level is about 5,000,000 square feet, or 
110 acres. At mean low water (see plate 1) the water-surface measures only 
1,400 feet from north to south and 1,700 feet from east to west, the total area 
at this level being about 2,000,000 square feet, or 45.5 acres. Ata level of 1 foot 
below mean low water the water-surface measures less than 700 feet from north 
to south, and a little more than this from east to west. At this level, however, 
there is a long tide-basin near the west side of the harbor, which is connected 
with the center of the harbor by a long tide-stream that sweeps around near the 
northwest corner of the harbor. The total area of water-surface when the tide 
is at this level is reduced to about 750,000 square feet, or 1% acres. That is, 
at such an extreme low tide, less than one-sixth of the bottom of the harbor is 
covered by water. 

The deepest part of the harbor has a bottom at but 7 or 7.5 feet below mean 
low water, and even this depth is found only over an area little more than 100 
feet in diameter. This area lies between 1,340 and 1,470 north and 500 and 
610 east. The bottom of the harbor is covered over most of its area by a thick 
layer of fine silt, which is slightly grayish on the surface, but dense black 
below the upper millimeter or two. The thickness of this black mud differs in 
different parts of the harbor. Near the shores there may be only a few inches, 
or at most a foot, while near the center of the harbor (e. g., at 1,800 north by 
0 east) a steel sounding-rod may be pushed down 9 or 10 feet below the surface 

of the mud before reaching the hard gravel bottom. Since the surface of the 
mud at the point referred to is but little below mean low-water level, the gravel 
bottom is here 9 or 10 feet below mean low water. 

It is worthy of note that at that part of the harbor where the water is 
deepest (eé. g., near 1,400 north by 600 east) the bottom is of sand, gravel, or 
shells, and is only about 7 feet below mean low water. This is evidently due 
to the fact that this part of the harbor is in the line of the swift current which 
carries on with it all but the coarsest particles. On the contrary, all the parts 
of the harbor bottom about this depression, except on the line joining it with the 
main stream and with the Inlet, 7. ¢., all parts outside the strongest current, are 
being filled up with the finer silt carried by the more slowly moving water. It 
is evident that Zostera plays an important part in retarding the tidal currents 
flowing over the harbor bottom to and from the Inlet. 

The silting up of the harbor is due partly to the remains of organisms 
growing in it, partly to material brought down by the fresh-water streams 
running into it. A relatively considerable amount of material is also brought 
in by the flood tides from the Outer Harbor. Part of this may evidently be 
material carried out by the last ebb tide, but part of it may come from other 
streams emptying into the Outer Harbor or may be eroded from the edges of the 
tide channel. The filling up of the Inner Harbor is going on at a rather rapid 
rate. In some localities, where the presence of Zostera or of the very numerous 


TOPOGRAPHY OF THE HARBOR ut 


mussels slows the movement of the water, the bottom may be built up an inch, 
or, locally, even several inches in a year. 

The only considerable areas of the harbor bottom below 1.5 feet which are 
at present covered by coarser materials are: the main channel of the Inlet, the 
deep hole at 1,400 north by 600 east, parts of the channel of the main fresh- 
water stream, and the bars on each side of the latter at 200 north and at 500 to 
600 east. ‘The main channel and deep hole have a bottom of gravel and bits of 
shell. The bars have a bottom often made up of alternate layers of mud and 
gravel. Because of the thinness of the gravel layers one often breaks through 
in attempting to walk over this part of the harbor bottom. These gravel layers 
are evidently spread over the constantly accumulating deposit of silt by the 
swifter current of the stream in times of flood. The bottom of the stream 
itself, from 0 to 580 south, is of gravel or small boulders in the shallow parts 
and of soft mud in the deeper holes. A small area with gravel bottom is found 
opposite the mouth of each small fresh-water rivulet along the shores of the 
harbor (indicated by FW on plate 1). These are but a foot or two in width, and 
often reach only half-way down the beach toward low-water mark. This is 
probably due to the fact that the bottom from the 2-foot level downward is so 
extremely flat that the water spreads out over it in very small, slowly moving 
rivulets (plate 118); that the masses of Ulva present turn the water or dam it, 
now at one point and now at another; and that such minute channels as are cut 
out of the mud during the short exposure of this low-lying bottom at low tide are 
filled in by wash of waves and by new deposits of silt when the tide rises. 

The boundary, or shore, of the harbor at the 8-foot level is in part natural, or 
undisturbed, and in part formed by artificial walls or wharves. The water-line 
of the natural shore at 8 feet is indicated on the map by a heavy solid line, 
usually more or less wavy, and marked frequently with a figure 8. The wharf- 
line is indicated by a similar heavy line, with short cross-lines added on one side. 
This line is generally more angular and straight, and not wavy. 

Beginning on the east side, we find the harbor bordered by vertical-walled 
stone wharves, practically all the way from the north end at 2,800 north, down 
to the old mill, at 500 north and 1,000 east. Along most of this distance, 1. e., 
from 2,200 north to the mill, as indicated on plate 1, the harbor bottom at the 
foot of the wall is at about the 1.5-foot level, while the wall extends up to a level 
of 8.5 or 9 feet (plate 111 B). South of the mill for 300 feet there is a sloping 
shore or beach between the 6 and 8 foot tide-levels, which is sparsely covered with 
gravel in some parts (plate 1vB). In other parts there is between these levels a 
sandy or peaty soil, of from 3 to 6 inches in depth, covered with Spartina patens, 
Juncus Gerardi, and other more thinly scattered species. From about 200 north 
to 100 south, the water’s edge, at high tide, les at the foot of the bank of a fresh- 
water canal. This bank is densely overgrown with shrubs and small trees. The 
level of the fresh water in the canal, during the five years of this investigation, 
was about 25 feet above mean low water. 

The 8-foot tide-line, from 160 south by 1,200 east, runs across a nearly flat 
eestuarial marsh, which for brevity we shall call the “ Marsh.” The line then 
runs west and northwest to 60 south by 1,000 east, then irregularly southwest, 
south, and westward to the road embankment at 575 south by 850 east. The 
western boundary of the harbor at the 8-foot level, from 625 south to 680 east, 
runs northward and northwestward, with a gravelly or narrow marshy shore, to 


12 THE RELATION OF PLANTS TO TIDE-LEVELS 


1%0 south by 380 east. From here northward to 20 south, then west to 0 east, 
and from thence northward and westward to 550 north and 230 west, the harbor 
is bounded by the stone walls of a tide-pool, then further on by the walls of the 
wharves along the south and west sides of the harbor. 

The western shore of the harbor, from 550 north to 2,250 north, is a rather 
steep, gravelly beach. The only exceptions to this are the stone wharf, with 
wooden piles, from 1,070 north to 1,220 north, a stone wall from 1,410 north to 
1,560 north, and two stone and wooden wharves from 2,080 north to 2,250 north. 
From 2,250 north this shore is muddy and is covered rather completely with 
Spartina glabra alterniflora up to the extreme northwest corner of the harbor 
near 2,600 north by 1,000 west. 

The Spit, which is 100 to 175 feet in width, and has an elevation of from 
10 to 12 feet above mean low water, forms the northern boundary of the harbor. 
The south beach of this Spit, between the 6.5 and 8 foot tide-lines, differs in 
character in different parts of its extent. From 1,000 west to 700 west the 
shore is of sandy loam, very flat, and covered with a dense growth, made up 
almost entirely of Spartina patens and Distichlis spicata. From %00 west 
to about 300 east, the beach is steeper and often nearly bare for considerable 
stretches (plate Iva). Where covered at all it is usually by small patches of 
Spartina patens, Sueda, or Salicornia. From 300 east to 900 east, the similar 
gravelly beach is covered, often completely up to 7.5 feet, by a dense growth of 
Spartina, Distichlis, Sueda, or Salicornia. Any one of these may occur locally 
in a pure stand, or, in other places, all may be more or less mixed together. 
Among these seed plants, on the bases of their stems, or on the gravel and sand 
of the otherwise bare portions of the beach, dense mats of incrusting alge of 
many species occur in patches a yard wide and several yards long, giving the 
beach a dark greenish or black color. These types of vegetation will be described 
_in detail later. 

The extreme eastern end of the Spit, beyond 825 east, is entirely bare between 
the 7-foot and the 8-foot levels, being essentially similar, except for the finer 
sand of which it is made up, to the wave-beaten outer side of the Spit at this 
same level. 


3. TIDE-LEVELS; MODE OF DETERMINING HEIGHT AND RATE OF RISE 
AND FALL OF TIDES. 

One of the primary facts we wished to determine concerning the habitat ot 
each species of plant growing in our area was the position of this habitat with 
reference to the tide-limits. Thus only could we determine how long, in each 
24 hours, the particular habitat is submerged and how long exposed to air, 
sun, and rain. Our aim was to discover just how definitely the distribution of 
beach and marsh plants is dependent upon the relative times of submergence 
and exposure of the plant-shoot and of the substratum upon which it is 
growing. 

The first step in accurately determining the relative times of submergence 
and exposure of any particular zone of beach or bottom is to establish a 
standard datum-level from which to measure the height of tides. This was 
done by placing a graduated tide-stake near the middle of the harbor, with its 
zero-point at mean low water. This stake was planted on a very quiet day, 
when, according to the Tide Tables of-the Coast and Geodetic Survey, the 


TIDE-LEVELS 13 


lowest stage of the tide was expected to reach exactly to mean low water. The 
correctness of this standard was checked later by other observations of the 
tide-level at both low and high water, and also, on quiet days, by comparing the 
level recorded on our stake with that predicted by the Tide Tables. This stake 
was graduated to feet and tenths of a foot for 2 feet below and 9 feet above 
the zero-point. 

When this standard tide-stake was once established, other similar graduated 
stakes were placed by the wharves on the east and west sides of the harbor, 
where records of the rise and fall of the water could be more readily made.” 
Stakes were also placed near the dense growths of alg and other plants whose 
distribution was to be studied. A permanent reference level or benchmark 
was cut into a stone on the northeast corner of the foundation of the Biologicai 
Laboratory, at 14 feet above mean low water. Records of rise and fall of the 
tides were made by noting the time the water reached each foot and half-foot 
mark on the tide-stake. Just before and after low water and high water the 
record was made for each tenth of a foot. This gives a more satisfactory 
record than that obtained by noting the height of the water at each interval 
of 10 or 15 minutes, since the contour-lines between tide-marks on the beach 
and marsh were determined for each half-foot interval. The records of the 
rise and fall of tide at the standard tide-stake were usually begun at or just 
before low water, and were continued through the rise to high water and 
through the succeeding fall to the next low water. In some cases the record 
was continued for 22 or 24 hours, in order to get the daily variations or 
differences in the height of low water and of high water in the two successive 
tides of each day. 

In the tide-curves here given, distances along the vertical axis indicate the 
height of the water above mean low water, in tenths of a foot, except at the 
middle and straighter part of the curve. Horizontal distances indicate time 
in intervals of tenths of an hour. The curve published in plate v1 shows a 
rather slowly ascending rise, taking nearly 2 hours, from low water at —0.2 
foot to +1 foot; a steep, nearly straight curve, taking 2.5 or 3 hours, from 
1 foot up to 6 feet; a very slow and irregular rise, taking about 2 hours, from 
6 feet to 7 or 7.5 feet. On the descent there is a slow and somewhat irregular 
fall from 7 to 6 feet or from 7.5 to 6.5 feet, lasting about an hour and a half; 
then follows a rapid descent to 2 feet, taking but 3 hours, and finally a slower 
fall from 2 feet to 0.2 foot in the morning tide or to 0.5 foot in the afternoon 
tide. This fall of 1.5 or 2.2 feet takes 2.5 hours, or nearly as long as is required 
for the drop of the 4 or 4.5 feet next above. The flattening of the curve on 
this side of low water is even more marked than that shown on the rise. 

In a confined harbor with a narrow inlet and with a surface area that may 
change very considerably with a slight change in level, it is to be expected that 
the tide-curve will show marked irregularities. As a matter of fact, the whole 
rise up to 6.5 feet gives a very regular curve. As one watches the rise of the 
water, however, between 6 and 7.5 or 8 feet, he sees the water remain almost 
constant at one level for many seconds or even two or more minutes, and then, 
suddenly, in a minute or less, go up a tenth of a foot. The record for the 
night tide, given in the curve on plate v1, shows this sort of irregularity very 


* See footnote on p. 133. 


14 THE RELATION OF PLANTS TO TIDE-LEVELS 


clearly, between 7 and 7.5 feet, in both rise and fall. This record was taken on 
a night when the water was so quiet as to insure accuracy, and the irregularities 
referred to are thus not at all due to waves or other local irregularities in level. 

An examination of the map shows that the 1.5-foot contour is widely 
separated~horizontally from the zero or mean low-water contour. That is, 
the area of the harbor bottom to be covered increases with great rapidity as the 
water rises from 0 to 1.5 or 2 feet. This seems evidently part of the explanation 
of the slow rise shown by the start of the curve in plate vi. On the other hand, 
the horizontal distance between the 2 and 6-foot contours is relatively small, 
which is probably related to the steepness of the curve between 2 and 6 feet. 
While the 6 and 8-foot contours are close together about much of the harbor, 
they are widely separated on the Marsh at the head of the harbor. This 
probably is a partial explanation of the flattening of the top of the tide-curve. 
It must be kept in mind, however, that the form of the tide-curve in the Outer 
Harbor, or the varying cross-section of the Inlet, may be concerned in deter- 
mining the form of the curve for the Inner Harbor. In fact, published curves 
for the tides of more open water show that there is often a flat crest and trough, 
even at the open shore of the ocean. (See Darwin 1910.) 

The matter of primary importance for us is the actual form of the curve for 
this particular harbor, without regard to the ultimate causes of this form. It 
will become evident, however, that those factors that determine the time at 
which the water reaches and leaves a given level on the beach give the time of 
submergence and exposure and determine, in part at least, which plants shall 
grow at that level. 

One can easily determine the time of submergence or exposure of any given 
level along the beach or wharf by consulting the tide-curves. This can also 
be calculated by subtracting the time of submergence from the time between 
one low water and the next following low water. The latter time varies from 
less than 12 hours, in the case of spring tides, to 13 hours, in the case of neap 
tides, the average interval being not far from 12.5 hours. Table A (p. 135) 
gives the average time of submergence and exposure for various levels from 
0 to 8 feet. This will be useful for reference when we come to describe the 
distribution of the plants of the harbor. 

A comparison of curves or records for neap and spring tides shows that 
the time of daily submergence of levels below 2 feet and that of emergence of 
levels above 6 feet is decidedly greater during neap tides than during spring 
tides. On the other hand, for levels between 2 feet and 6 feet the time of sub- 
mergence, like the emergence, is practically the same for both kinds of tide. 
This latter fact is clearly indicated by the straightness of both sides of the tide- 
curve between the levels mentioned. This means, of course, that plants growing 
in this zone of about 4 feet in vertical width have a practically constant propor- 
tion of daily submergence and exposure, from end to end of the growing season. 
On the beaches it is just this zone that is dominated by Spartina glabra alterni- 
flora (plate vit A). | 

The plants of the harbor bottom below the 2-foot level and those of the 
beach above the 6-foot level are subject to much greater variation in the 
proportion of daily submergence and exposure. It might be assumed that 
this variation within each fortnightly period, ¢. e., within each set of tides, is 


TIDE-LEVELS 1D 


of no importance, and that the total times of submergence and exposure 
each fortnight, or for the whole growing season, are the decisive factors limit- 
ing the distribution of a plant. There is, however, good evidence that the long 
exposure during an extreme low tide on a clear, hot day may result fatally to 
plants that have flourished during average tides, e. g., Ulva seems often to be 
killed off by long exposure and drying up, after the draining off of the water 
from the underlying mud. 


TIDE-LINES. 
After the standard tide-stake and the Reith stakes were established, the 
method of determining the position of the 5, 6, 7, and 8 foot contours, or 


tide-lines, on the beach was as follows: 

An ohaserer stationed near a tide-stake gave etna by a whistle or flag when 
the water had risen to within 1 inch of the level to be marked, another signal 
when the water reached the exact level, and a third when it reached 1 inch 
above this. One or more workers on the beach, with bundles of stakes, each 
marked with the height of the level that was being determined, began to set 
these at 50-foot intervals along the beach. On hearing the first whistle, stakes 
were set at an estimated height of 1 inch vertically above the water-line. At 
the second signal the stakes were set exactly at the water’s edge. At the time 
of the third signal they were set in water 1 inch deep. By knowing the rate of the 
rise of water at that stage of the tide, the stakes could be set nearer and nearer 
the water’s edge after the first signal, and deeper and deeper in the water as the 
third signal approached. Thus the exact position of the water-line was marked 
quite accurately by stakes for each foot from the 5-foot level to the 8-foot level. 
The position of each stake was then plotted on the map, and with map in hand 
in the field these points were connected up to form the contour-lines. 

The contours of the Marsh and Sand-spit, above 8 feet, were determined 
by a surveyor’s level. The —1-foot, 0-foot, +1-foot and +-1.5-foot contours 
were plotted by noting, when the water was at each of these levels, the point of 
intersection of the water-line with each of the longitudinal and transverse 
range-lines. The contours between —2 feet and —? feet were determined by 
soundings. 

The stakes marking the 6-foot, 7-foot, and 8-foot tide-lines were left on the 
beach throughout the season. By the aid of these it was possible accurately 
to determine the exact vertical distribution of the plants of beach and Marsh. 
The vertical distribution of plants on each wharf was determined by the 
graduated tide-stake beside it. 


Ii]. PLANT ASSOCIATIONS; CHARACTERIZATION OF THE 
BELTS OR ZONES OF VEGETATION AND THEIR 
DISTRIBUTION. 


We will begin our discussion of the vegetation with a descriptive account of 
the plant associations found in the harbor, noting their composition and distri- 
bution. Then will follow a general discussion of the factors determining 
distribution, and a list of all plants found, showing the distribution of each 
species and the relation of each to the factors affecting its distribution. 

In defining the limits of the zones of vegetation in this harbor we shall use 
the term “ littoral” in a more definite way than we have found it used by other 
writers on the distribution of marine plants (see Lorenz, 1863; Kjellman, 
1877; and Warming, 1906). We shall designate as littoral the zone extending 
from mean low water up to mean high water, which, for our harbor, is a zone 
8 feet, or more exactly of 7.8 feet in vertical width. The littoral zone of this 
harbor is distinguished, in a manner determined by the vegetation itself, into 
lower littoral, mid-littoral, and upper littoral subzones. The region just below 
mean low-water level, of which 1.5 feet may be exposed at extremely low tides, 
will be referred to as the sublittoral zone. The zone of 3 or 4 feet above mean 
high water, which may be flooded by occasional high tides or storm tides, will 
be called the supralittoral zone. 

The most clearly marked primary vegetational groups or plant associations 
in the harbor are these: 

(1) Plankton, made up of the plants floating at the surface in a living 
condition, chiefly diatoms and Peridinez. 

(2) Plants at the bottom of the harbor, between the —5-foot and the +1.5- 
foot levels. These occupy the soft, muddy, sandy, or pebbly bottom, or are 
epiphytic upon plants which grow on this bottom. The shifting pebbly or 
shelly bottom in the deepest part of the harbor is bare of fixed vegetation up to 
the —5-foot level mentioned, which thus marks the lower boundary of the belt 
under discussion. The upper limit of this belt is at the +-1.5-foot level, where 
the soft mud, forming most of the bottom, is succeeded by a soil that is rendered 
firm by the close network of rhizomes and roots of Spartina glabra, which 
occupies the next succeeding belt on shore. This lower limit of S. glabra, with 
its sudden change in elevation of the bottom, in character of soil, and in the 
vegetation covering it, forms a very prominent topographic boundary. It is 
therefore indicated on our topographic map. 

(3) The mid-littoral belt of vegetation occupies the shore between the 1.5- 
foot and 6.5-foot levels. On muddy shores a fringing marsh of Spartina glabra © 
dominates between these levels to the exclusion of all other seed plants, save a 
few small groups of the inconspicuous umbellifer Lileopsis lineata. Numerous 
alge, however, are found on the mud between the stalks of the Spartina. 
Many of them are species not found elsewhere, and most of them are associated 
in mats or felts of a sort not occurring in other locations except in the next 

16 


PLATE Il 





A. Looking over Harbor Bottom at Low Water, from 200 North < 600 East 
toward 2,600 North>400 West, showing Ulva covering Bottom, and Tide 
Channels from Creek. 





B. Looking over Harbor Bottom from 100 North * 40 West to 600 North x 1,000 
East, showing Ulva on Bottom and Tide Channels from Tide Pond; at 
Right Middle Ground the Northernmost Tongue of Spartina glabra alterni- 
flora from Marsh. 


LAING! 


“Thy or? 


bm as 
FS 
‘ 


arr 
7 a 


i 





PLANT ASSOCIATIONS ahy) 


higher belt, where these associations have a somewhat different make-up. On 
stony substrata within the limits of this belt, which are confined practically to 
the walls of the wharves, we find a nearly continuous rockweed association. This 
is dominated by Fucus vesiculosus, F’. evanescens, and Ascophyllum nodosum, 
but it embraces also a considerable number of smaller alge of all classes, many 
of them very numerous. A few of the latter are found on the fringing marsh 
also, but most of them are not. 

(4) The upper littoral belt extends from 6.5 feet to 8 feet. On gravelly, 
well-drained portions of the shore this level is usually dominated by Salicornia 
or Sueda, and less frequently by Spartina patens, often mixed with Distichls. 
These are the areas that we have called “upper littoral beach.” On flat, 
poorly-drained shore with peat-like soil we find an upper littoral marsh 
dominated by Spartina patens, by Distichlis spicata, or by Juncus Gerardi. 
Where the soil is more or less saturated with fresh water Scirpus americanus 
dominates. This apparently corresponds in most respects to the “ salt- 
meadow ” of Warming. 

(5) The supra-littoral belt of vegetation extends from high-water level at 
8 feet upward as far as the direct influence of the sea is felt by the vegetation, 
which is often 10 feet and on the Spit up to 12 feet. In this belt also we find 
two distinct associations, determined by the character of the soil, especially by 
its drainage. In sandy, well-drained portions, which are found only on the 
Spit, we find a supra-littoral beach, or storm beach, dominated by Ammophila 
arenaria, with which are associated three or four prominent species of dico- 
tyledons and a score of other species, chiefly seed plants, of less frequent 
occurrence. On flat, undrained portions of the shore between these levels, where 
the peaty soil is subjected to submergence by spring tides, and is in many places 
kept continually moist by subterranean fresh water, we have a supra-littoral 
marsh, the “ higher littoral marsh” of Warming. This sort of marsh is well- 
developed only at the head of the harbor. Near the 8-foot level the soil-water 
is brackish or nearly salt, while near the upper limit of this marsh at the 9-foot 
level the soil-water is practically fresh, at least during the growing-season. 
In consequence, evidently, of this difference in salinity, and in other soil 
characters, as well as in elevation, the vegetation differs greatly in different 
parts of the marsh. The lower, more saline portions are dominated by Spartina 
patens or by Juncus Gerards, while fresher areas are characterized by Scirpus 
americanus, and the highest parts are occupied chiefly by Aspidium thelypteris. 


1. THE PLANKTON. 


The plant constituents of the plankton of the Inner Harbor consist of a 
relatively few species of diatoms of the genera Melosira and Navicula, and a few 
species of Peridinaces. Of the latter one species of Glenodinium often occurs in 
such numbers, over areas of scores of square meters, and to a depth of 0.5 meter 
or more, as to color the water a deep brown. This condition was frequently 
noted two or three times a summer, and often lasted for several successive days. 
Professor C. B. Davenport informs us that this or a similar species of the 
Peridines is sometimes so abundant in September as to kill many of the fish 
in the harbor by clogging their gills. The time at our disposal did not suffice 
for a detailed study of the plankton and its daily and seasonal variation. 

2 


18 THE RELATION OF PLANTS TO TIDE-LEVELS 


2. THE BOTTOM VEGETATION OF THE HARBOR FROM -5 TO +1.5 FEET 
(THE SUB LITTORAL AND LOWER LITTORAL BELTS). 

The present belt includes 1.5 feet of the lower part of what Kjellman calls 
the “ littoral region,” 1. e., of the strip between low and high tide marks. It 
also includes 5 feet vertically of bottom below the mean low-water level, 4. ¢., 
5 feet of what Lorenz calls the “ submerged littoral region.” 

The plants forming the bottom vegetation of this harbor consist of (A) plants 
of the loose soil; (B) algz attached to stones or shells; (C) epiphytes living 
chiefly on members of group A. 


A. PLANTS ON LOOSE SOIL (THE ENHALID FORMATION OF WARMING). 


This formation includes two seed plants, Zostera and Ruppia, which are 
rooted in the soft bottom, and only two important alge, Ulva lactuca and 
Enteromorpha clathrata. Most of these latter are unattached, and either 
simply rest on the bottom or are weighted down by mud or mussels. The Ulva 
grows in sheets, the Hnteromorpha in tangles. In looking down on the bottom 
of the harbor from the neighboring hills at low tide, 1. e., with the water- 
surface at —1 foot, the bottom over most of its area appears green in color. 
This green color is due to the presence of the more or less uniform covering 
either of Ulva lactuca or of Zostera marina, or, on some smaller areas, of 
Enteromorpha clathrata. The most considerable bare area on the part of the 
bottom, exposed by the lowest tides, is that at the north and northwest portions 
of the harbor, which lies between the —1-foot level and the 2-foot level. Besides 
this there are two or three narrow strips, 12 to 15 feet wide, and trending more 
or less northward from the mouth of the main fresh-water stream at 200 north 
by 550 east, which are rather constantly bare. (See plates 11 and vit.) There 
are other smaller changeable bare spots on various parts of we bottom outside 

the Zostera belt. 

Of those portions of the harbor bottom still covered a the water is at 
—1 foot, the bottom of the tide-channel starting near the wharf of the Research 
Laboratory at 1,100 north by 400 west, and emptying into the deep hole at 1,400 
north by 400 east, is nearly bare of Ulva and Zostera. Likewise, the greater por- 
tion of the deep hole itself, and of the channel leading from it to the Outer 
Harbor, have a rather bare, sandy, shelly, or pebbly bottom, except for that 
portion to the east and south of the deep spot which is indicated on the map as 
covered with Zostera. The plants of Ulva found under these more swiftly 
moving waters are small attached plants which are evidently being carried along 
with their supports. ‘The area occupied by a dense growth of Zostera is indi- 
cated on the map by a wavy outline marked Z. Its distribution will later be 
described in some detail. 

The rest of the harbor bottom below the 1.5-foot level, aside from the bare 
areas mentioned above, is rather completely covered with Ulva. This Ulva 
occurs in the form of innumerable detached flattish, or crumpled, or bullate 
and often perforate and ragged sheets, of all sizes from a few decimeters to 10 
meters across. The distribution of much of this Ulva over the bottom is more 
or less inconstant. Often the bottom is covered completely for hundreds of 
square meters, e. g., 400 to 1,000 north by 200 west to 400 east. In other 
portions of the harbor only one-half or three-fourths of the bottom is actually 
hidden by the Ulva, e. g., near the west side at 0 to 600 north, or near 200 north 
by 400 west. 


ENHALID FORMATION 19 


On closer examination of the Ulva plants of the harbor, it is found that 
practically the only attached plants present are relatively small, being 1 to 5 
or 6 dm. across. These are found chiefly on pebbles and shells along the sides 
of the channel of the Inlet leading to the Outer Harbor and beside the main 
fresh-water streams, e. g., at 200 north by 550 east, at 200 north by 950 east, 
at 2,380 north by 980 west. A few attached plants were found on stakes, on 
buoys, and on shells of living mussels in various parts of the harbor. A very 
few attached plants occur on the rhizomes of Spartina glabra and on stones 
of the wharves in the next higher belt. The widespread, though sparse, dis- 
tribution of these plants in the harbor probably indicates that zoospores are 
abundant there. The practical absence of attached plants from most parts of 
the harbor bottom is evidently due to the lack of proper substrata, except where 
entering streams or tidal currents leave a surface of coarse particles on the 
bottom. ‘The detached sheets of Ulva covering the bottom may become second- 
arily fixed by the attachment to them of numerous mussels or of snails. In 
other cases parts of the sheet of Ulva may be buried, and thus fixed, by the mud 
shifted by water-currents or by burrowing animals. 

The general distribution of Ulva described above is that found each summer, 
in July and August, for six years past. The exact size and position of the 
minor bare spots in the Ulva zone changes from year to year, and in fact from 
week to week or even from day to day, due to the movement of the free Ulva 
by water-currents. In December 1912 the Ulva was about as abundant in the 
harbor as in summer. The bottom of the harbor was reported as nearly bare of 
Ulva in February 1913. In the following April, however, Dr. A. F. Blakeslee 
found many small sheets on the mud at the south end of the harbor. 

A somewhat detailed examination of the harbor in April 1911 showed that 
the bottom above mean low water is much less completely covered with detached 
Ulva than in midsummer. In fact, large sheets were almost wanting in those 
parts of the harbor that could be examined. On the other hand, a search for 
attached Ulva, in the places where it occurs in summer, showed that it was far 
more abundant in April. On the east side of the channel to the Outer Harbor, 
for example, there were thousands of attached plants of Ulva, of all sizes up 
to 1.5 or rarely 2 dm. across, and all of them were evidently growing vigorously. 
In July 1911 these same areas bore a much smaller number of plants, of which 
the largest in the middle of the channel were about 6 or 8 dm. long. In the 
inrushing tide near the Inlet one may always find plants of Ulva or parts of 
plants floating in with the current, and thus being carried to the quiet parts 
of the Inner Harbor, many of them settling on the bottom with the next fall 
of the tide. These floating sheets are evidently plants that have been broken 
off from their supports or substrata in the Inlet and elsewhere where young 
plants are developed abundantly. The maximum size of fixed plants found in 
the Inlet in July 1911 (about 6 dm.), is probably the size at which the tensile 
strength of the base of the plant is just able to withstand the strain of the 
swiftest tidal currents. Plants larger than this are torn off, or carried away 
with their supports, as even smaller ones also may be, and are thus added to 
the covering of the bottom of the Inner Harbor. 

It seems clear from the facts just mentioned that the large, free sheets of 
Ulva in the Inner Harbor are developed by the continued growth and crump- 
ling of the relatively small and flat plants that have been torn from their 


20 THE RELATION OF PLANTS TO TIDE-LEVELS 


original attachment in the Inlet and on other pebbly bottoms of the harbor. 
Such detached plants of Ulva do not necessarily lodge within the Ulva zone 
the first time that they are washed into the harbor; neither do they stay 
indefinitely at the point where they first lodge. Even larger sheets that have 
been resting on the bottom for days or weeks may be moved about by the water 
in one of two ways. In the first place, sheets that lie on the flats bordering the 
tide-channels may be rolled up by the tidal current of large, swiftly flowing 
spring tides, and gather additional sheets as they are tumbled along over the 
flats, until rolls are formed 0.5 meter in diameter and 2 or 3 meters long. 
These rolls have been seen to roll for 40 or 50 meters over the shoals near 
2,000 north by 200 to 800 east. Such rolls may evidently either be carried out 
to the Outer Harbor, or be broken up again, with considerable tearing of the 
sheets, and the fragments floated back to be redistributed over the bottom of 
the harbor. The long bare strips of bottom noted above are often merely the 
trails of such rolls. 

The second mode of transportation is one that is seen on days that are bright 
and windy, during extreme low water, especially of spring tides. ‘The long 
exposure of the Ulva-covered parts of the bottom at such times allows the 
water to drain off and permits air, and probably other gases from the underlying 
mud, to collect under the coarsely crumpled sheets. With the rising of the 
tide these sheets or portions of sheets of Ulva are floated up 2 or 3 feet off the 
bottom or even to the surface at high water, and finally, becoming entirely 
free from the bottom, they are blown by the wind along the surface of the water. 
Such floating plants may drift about the harbor and then out through the 
Inlet with the next fall of the tide, or they may settle in new places on the 
bottom, or with stronger winds they are sometimes blown to the shore, where 
they may become tangled among the reed grass or drifted on the beach. 
Windrows of Ulva thus formed are often found on the beaches between the 
3 and 8 foot levels, or caught in the Spartina glabra, sometimes covering many 
square meters. There the plants finally die from exposure to the sun and rain. 
Just what part this floating of the Ulva may play in finally denuding the 
bottom of the harbor was not determined by an actual counting of the floating 
sheets and a measurement of their sizes, but it is evident that it may be a very 
considerable one. It is, however, probably small in comparison with the 
destruction and transportation of Ulva accomplished by the ice, though the 
importance of this factor is also undetermined, since we have not been able to 
study the harbor in detail in winter. 

If the history of the sheets of free Ulva found on the harbor bottom in July 
is that which has just been suggested, then it is certain that the growth of 
those plants which settle in favorable places must be very rapid. One of the 
larger sheets measured in August was found to be 10 meters long and about 
equally broad. The production of such a plant as this in 3 or 4 months from 
one 6 or 8 inches across indicates the remarkable average rate of radial growth | 
at all parts of the margin to be 30 or 40 mm. per day. 

Assuming that the largest plant seen in July 1911, located just aside from 
the swiftest current, had come from the largest plants seen in April 1911, the 
rate of growth would average only 8 or 10 mm. per day. Actual measurements 
by Miss Stella G. Streeter of the rate of growth of somewhat smaller plants 
growing under natural conditions in July and August 1910 give a daily incre- 


ENHALID FORMATION 21 


ment much smaller than this. For example, a series of young plants averaging 
26 mm. in length increased to an average length of 55 mm. in 20 days. The 
average daily rate of growth was 1.5 mm. and the maximum daily increment 
was 2 mm. 

It is of course possible that the large sheets of Ulva may winter over in some 
of the deeper, more protected parts of the Inner Harbor, and less probable 
that they may be washed in from the Outer Harbor. The rates of growth actually 
observed indicate that the largest of these plants can not be produced from 
spores in a single season. It is hoped that observations now under way may 
definitely determine the age of these larger sheets. It is of course possible 
that the larger amount of sewage present in the water in summer, during the 
session of the Biological Laboratory, may enable the Ulva to grow more 
rapidly than in winter or spring. (See Cotton, 1911, and Letts and Richards, 
1911.) 

The lower limit of distribution of attached plants of Ulva in the Inner 
Harbor is very near the mean low-water level. Plants which are drifting with 
their supports and torn off bits may be found at greater depths, but we have 
not determined how long they can persist there, and there is no adequate 
evidence that zoospores of Ulva develop to young plants at levels more than 6 
inches below mean low water. Why this species is confined to levels which are 
exposed to air and light has not been determined, but apparently it is due to 
the direct effect of some physical factor, since there are, in most places, no 
competitors, and there are, at least in some places, suitable substrata for attach- 
ment some distance below this limit. 

Since Ulva occurs in the next higher zone, we may discuss the factors 
determining its upper limit in that connection. 

Ulva probably influences the distribution of other plants only as it forms 
the substratum for certain epiphytic diatoms and a few species of blue-green 
alge, of which latter Spirulina is the only form of any importance. It is 
probable also that the smooth sheets of Ulva lying on the mud may prevent 
_ young seedlings and broken off bits of Zostera from getting a hold in the mud. 
Finally, the floating masses of Ulva, like other flood trash, may smother out 
many square yards of Spartina patens, or other plants already established on 
the marshes, by settling on them with the fall of the tide. The bare patches 
so formed often become re-covered first with Vaucheria or seedling Salicornias, 
as will be described later. 

Enteromorpha clathrata: This plant, as we shall find, is not by any means 
confined within the 1.5-foot contour line, but may be found as high as the 6 or 
6.5-foot level. It does, however, occur far more abundantly on the bottom of 
the harbor than elsewhere. As one rows over the harbor just before low water 
on a quiet day, he will see on the leaves of Zostera numerous tufts of sparsely 
branched, crinkled, green, tubular filaments, 1 or 2 mm. in diameter, and com- 
monly from 5 to 20 cm. in length. These are the young plants of probably a 
few weeks growth of Hnteromorpha clathrata. Observations made in the 
Outer Harbor show that this species may grow from the zoospore to a length 
of 4 inches in as many weeks. After these plants have grown to 8 or 10 inches 
many of them, like the young plants of Ulva, are broken away from their 
supports and float about in the harbor, to finally grow into the great tangles 
that settle down on the Ulva and Zostera, sometimes covering dozens or scores 


2? THE RELATION OF PLANTS TO TIDE-LEVELS 


of square yards of the bottom. In the more quiet areas the Hnteromorpha may 
form tangles of considerable size while remaining attached to the Zostera on 
which it germinated. The later history of these tangles of Hnteromorpha is 
similar to that of the sheets of Ulva. They are often floated up by gases accu- 
mulated in the cavity of the tubular thread. They then drift about the harbor, 
to lodge on some new part of the bottom and continue active growth, or they may 
settle on the beach or on top of Spartina glabra. On the south shore of the Spit 
masses of H. clathrata with some intermingled Ulva may crush down 75 or 100 
square yards of Spartina, in some cases smothering out the rhizomes also and 
leaving a bare strip. Such tangles as lodge on the beach or on the salt reed-grass 
die and then break up and wash away or settle down to form part of the soil 
among Spartina stalks. Smaller bits of the living alga may settle on the mud 
between the Spartina stalks, or among pebbles on the beach above the Spartina, 
and there take part in the formation of the composite mats or felts of which 
other green or blue-green alge form the major part. Of its distribution there 
we shall have something to say when discussing the other alge of these higher 
levels. Despite the fact that it floats more readily because of the gases within 
its filaments, the freedom cf movement of Hnteromorpha is on the whole less 
than that of Ulva. Because of its filamentous form Hnteromorpha becomes 
more readily entangled with other objects on the bottom, and it is also more 
often weighted down by young mussels which become attached to it in 
thousands. On the bottom from the 6-inch to the 1.5-foot levels, where 
Zostera and mussels are usually wanting, the tangles of Hnteromorpha are also 
rare. The usual absence of Hnteromorpha lower than about 3 feet below mean 
low water seems also determined by the absence below this level of organisms 
such as Zostera and mussels, with which it may become entangled or weighted 
down. It is true that small mats of this alga are sometimes seen below the 
limit of the Zostera in the deep hole at 1,400 north, but these are apparently all 
in transit to or from the Inlet. Younger plants attached to stones are found all 
along the Inlet from 3 feet downward, some being found even in the deep hole. 
These plants must form an additional though relatively unimportant supply of 
free plants which may grow into tangles like the more numerous plants starting 
on the Zostera. 

Zostera marina: This “ eel-grass,’” because of its abundance, gives character 
to large areas of the harbor bottom at low tide, and also forms an important 
substratum on which grow several species of epiphytic alge. For this reason 
the region covered by a dense growth of Zostera has been indicated by a wavy 
outline on the map showing the topography of the harbor (plates 1 and xmir). 
The area so indicated is not by any means evenly covered with Zostera. In fact, 
many areas within this boundary which are several yards across may have but 
the barest sprinkling of this plant. Moreover, as is indicated on the map, there 
are numerous scattered or clustered and usually small plants of Zostera outside 
of this boundary. 

In the more vigorous patches of Zostera found in the Inner Harbor in July, 
the individual plants often have a rhizome 0.33 meter long and from 2 to 3.5 
or 4 mm. in diameter. It is made up of 15 or 20 internodes, and runs along 
horizontally 1 cm. or more below the surface of the mud. Each rhizome 
terminates in a floral shoot, and bears from 2 or 3 to as many as 5 or 6 leafy 
lateral shoots. These lateral shoots may branch two or three times above the 


ENHALID FORMATION 23 


mud, each of these branches consisting of from 12 to 20 short internodes, and 
bearing from 4 to 8 functional leaves. The width of these leaves varies from 
5 to 8 mm. and the longer of them are from 1 to 2 meters in length. The 
fertile, or floral, shoots of Zostera, at this season, vary in length from 50 cm. 
to 1.5 meters. Each consists of about 15 or 20 internodes, which are from 1.5 to 
2 mm. in diameter and from 5 to 20 cm long. Each node bears a leaf which 
is about 4 mm. wide and 15 cm. long. On older parts of the shoot nothing is 
left of the leaves but the sheath and perhaps a small bit of the blade. Inflores- 
cences in all stages of development are present on each fertile shoot, from 
floral rudiments just initiated at the top to spathes at the base from which the 
fruits have already been discharged. 

The densest stands of Zostera seen in the harbor are that east of the channel 
to the Outer Harbor, northeastward from 1,200 north by 800 east, those along 
the two banks of the tide-stream from 2,000 north by 400 west to the depression 
at 1,500 north by 300 east, and that on an area of several hundred square yards 
extent southwest of the deep hole about 900 north by 200 east. On these areas 
there may be from 500 to 2,000 leaf-clusters of Zostera to each square yard “ 
bottom. In other parts of ‘the Zostera region indicated on the map, e. g., 
much of the area near the main north-and-south axis from 1,000 north to 2, 000 
north, the stand of Zostera is far less dense, with an average ‘of 200 or 300 leaf- 
clusters per square yard. For some distance outside the indicated area, espe- 
cially to the north and west, plants of Zostera are very infrequent, perhaps 20 to 
100 small tufts to each square of the map, 7. ¢., to each 3,333 square yards. 

These tufts are mostly scattered and show but 2 or 3 to 10 or 12 leaf-clusters 
each. The extreme limit of distribution of Zostera is shown on plate x111 by the 
use of the letter Z, which is used as a symbol for indicating the position of 
outlying plants. These plants are usually small, being 1.5 to 6 dm. from the 
rhizome to tips of leaves, and their distribution varies somewhat from year to 
year. For example, numerous scattered plants of Zostera were found at 2,000 
north by 0 to 600 east in 1905 and 1906. From 1907 on, following the 
occupation of much of this area by beds of mussels (Mytilus edulis), Zostera 
has been nearly or quite wanting here. The presence of the mussels has 
evidently led to a gradual silting over of the bottom of this area, raising it to 
or above mean low water, which is probably a direct cause of the disappear- 
ance of Zostera. It may well be that the mussels also cause other changes in 
the soil, making it injurious to the Zostera, e. g., in the content of such gases 
as air, CO,, or H,S. Such changes may explain the disappearance of Zostera 
from bottom not continuously occupied by mussels that has not yet been raised 
above the usual upper limit of this plant. 

Though the horizontal distribution may seem decidedly irregular (plate x111), 
especially the scattered marginal tufts, the distribution in depth is pretty con- 
stantly limited. It is found at levels extending from mean low water down to 
3.5 feet below this. The parts of the harbor where Zostera occurs above the 
upper limit mentioned, are certain areas where bottom at 6 to 12 inches above 
mean low water is overflowed more or less at low tide by water from inflowing 
streams. For example, the southern prolongation of the Zostera area near 
600 north by 400 east overlaps the mean low-water line very considerably, and 
scattered outlying plants of Zostera are found as far south as 300 north by 
200 to 400 east or 275 north by 725 east, and even a few tufts near 210 north 


24 THE RELATION OF PLANTS TO TIDE-LEVELS 


by 500 east and at the 1.5-foot level. It seems evident from what has just been 
said that Zostera is excluded from bottom much above mean low water by its 
liability to death from exposure at low tide. In those places where it exceeds 
this usual upper limit it is protected from desiccation by water from streams, 
which runs over it at low tide. 

The environmental factors determining the lower limit of the Zostera have 
not been distinguished with absolute certainty. So far as could be discovered, 
from a study of the relatively short lower margin of the Zostera area about the 
deep hole, this plant does not encroach on bottom lower than that indicated, 
because this lower bottom is sandy or shelly. Such soils, in this harbor, are 
nearly always bare, no matter what the depth. In the few places where Zos- 
tera seems to be growing on such bottom, the use of a sounding-rod usually shows 
that there is a softer subsoil of mud, an inch or two below the surface. It seems 
likely that the Zostera in these spots originally became established on a mud 
bottom which later, by some change in water-currents, was covered by a layer 
of sand and shell fragments. Only a few plants, which had very short, narrow 
leaves, were found growing on an apparently pure sandy bottom. Possibly the 
turbid water of this harbor may make the light supply inadequate at greater 
depths. In the clearer water of Casco Bay, Maine, Zostera grows on soft 
bottom 10 feet below low-water mark, also in Great South Bay, New York. A 
similar distribution of Zostera is found in Carmel Bay, California. 

C. H. Ostenfeld (1909) has found a similar relative abundance and size of 
the Zostera (growing, however, in much deeper water), on sandy and on muddy 
bottoms of the coast of Denmark. He states (p. 33) that on the bare, firm, 
sandy bottom there is only a sparse growth of Zostera with short, narrow- 
leaved shoots, which are free from growths of epiphytic plants and of animals. 
On soft, muddy bottom, on the contrary, he finds a dense pure growth of 
Zostera with larger and broader leaves, which latter are occupied by many 
- epiphytic diatoms, brown and red alge, and various animals, e. g., hydroids, 
mollusca, bryozoans, and ascidians. On pebbly bottom, where the interspaces 
between pebbles and boulders are occupied by softer soil, Ostenfeld finds a 
“mixed Zostera vegetation” in which, on certain areas, Zostera grows in the 
mud, while the pebbles give fixing-points for Fucus, Laminaria, and other 
coarse brown and red alge. Another type of mixed Zostera vegetation is that 
mentioned by Ostenfeld as occurring in brackish waters with bottom of sandy 
mud, and is characterized by the abundance of the green alge Ulva, E'ntero- 
morpha, Cladophora rupestris, Chetomorpha linum along with Chara, Toly- 
pella, Lamprothamnus, and also the seed plants Ruppia, Zannichellia, and 
Potamogeton pectinatus. This last type is the one that approaches most 
nearly, on the whole, to the Zostera vegetation of the harbor we are studying. 
Perhaps the most striking difference between the two is the absence, from our 
area, of the Characeew and Potamogeton. The similarity will be clear when we 
consider the distribution of the alge of the harbor bottom. 

In our harbor the differences in the character of the bottom, and so the 
presence or absence of Zostera, seem primarily due to the differences in the 
swiftness of the water-currents. The bottom of the deep hole, and of the 
channels north of it, is of sand or gravel and particles of shell, with a few 
bits of organic material, all of which may be seen shifting with the current 
when the tide is swiftest. The only fixed plants seen here were Ceramiums, 


ENHALID FORMATION oo 


Polysiphonias, Rhabdonas, Ulvas, etc., which, with their anchoring pebbles, 
were evidently in transit through the Inlet. From a careful consideration of 
the conditions existing in the deeper portions of the harbor, it seems evident 
that the absence of Zostera is in some way determined by the swift tidal 
currents rushing over these portions. As there is no reason to believe that this 
current acts directly on the Zostera, it seems clear that the current acts by 
forming an unstable and sterile bottom on which Zostera can not establish 
itself. A merely sterile soil we would expect to be conquered by the gradual 
extension of Zostera into it, with an accompanying accumulation of organic 
matter about its shoots. We must conclude, therefore, that the downward 
spread of Zostera in this harbor is prevented by a shifting of the soil so frequent 
as to make it impossible for the out-pushing rhizomes to establish themselves 
and thus bind the soil. , 

Ostenfeld, in his study of Zostera in Danish waters, found that the shoots 
are perennial, and the leaves remain green all winter. The winter leaves of 
plants growing on mud bottom do not attain as great a length as leaves 
developed in summer. 

A somewhat similar retardation of growth in winter seems to occur at Cold 
Spring Harbor. Since our observations were confined largely to the months 
of July and August, we can not speak with certainty concerning the activities 
of the Zostera in winter. On April 7, 1911, however, an abundance of 
Zostera plants was found with most of the leaves only 1 or 2 dm. long, and 
evidently young, but also with older leaves a half meter or more in length. 
Plants collected in about the same locality on July 11, 1911, had leaves 2 
meters long. Many of these were dead and worn at the tip and seemed evidently 
more than 2 or 3 months old. Not many plants of Zostera were collected and 
measured in April 1911, but it seems probable, from the condition of the plants 
in the following July, that longer leaves would have been found by more 
thorough search in April. From all the evidence gathered we are led to 
conclude that while the longer leaves of Zostera plants may be torn off by waves 
and ice during the winter, the leaves of the more sheltered plants may often 
persist from fall to spring. This conclusion is strongly supported by the fact 
that the floral shoots certainly persist over winter. This is shown by the fact 
that floral shoots 90 cm. long and bearing fruits 3 to 4 mm. long were collected 
on April 4, 1913, by Dr. A. F. Blakeslee; also by the presence in early July of 
empty spathes on infloresences which higher up bear mature and young fruits 
and unopened flowers. On the Danish coast, according to Ostenfeld, the floral 
shoots are initiated in April and drop off the rootstock in the late fall. We are 
not prepared to suggest any causal explanation for this difference in behavior 
of the Zostera in these two localities, unless it be the more destructive effect of 
winter waves in the more open water where Ostenfeld’s plants grew. 

In brief summary of the facts concerning the distribution of Zostera in the 
Inner Harbor, we can say Zostera commonly occurs on bottom between mean 
low water and 3 feet below this. In one or two areas flooded by streams at low 
tide, a dense stand of Zostera may grow on bottom a few inches above mean low 
water. The extreme upper limit at which Zostera was found—a few plants 
only—is 1.5 feet, and the extreme lower limit is —4.5 feet. The species is 
almost entirely confined to muddy bottoms. 

The part played by Zostera as a substratum for epiphytic alge will be 
noted in discussing the distribution of the alge. 


26 THE RELATION OF PLANTS TO TIDE-LEVELS 


Ruppia maritima: This comparatively diminutive and delicate species is the 
only seed plant besides Zostera that is found on the bottom of the Inner Harbor 
below 1.5 feet. The characteristic mature plant of Ruppia, as it occurs in 
this harbor, is about 25 cm. long, and of 10 to 12 internodes varying in length 
from 20 to 70 mm. It has 8 to 10 functional leaves each 20 to 60 mm. long 
and 1 mm. wide. The plants flower freely at Cold Spring Harbor during July 
and August, but the stalk of the infloresences is short, rarely more than a few 
em. long, and therefore the flowers are not at the level of the water-surface 
except for about half an hour at the rise of the tide and a lke interval 
at its fall, 7. e., when the water-level is between 6 inches and 1.5 feet above 
mean low water. The plants flower and apparently fruit freely, as seedlings 
are rather frequently found. 

While Zostera is characteristic of an area lying below mean low water, 
Ruppra is practically confined to a vertically narrow belt between mean low 
water and 1.25 feet. The extreme limits are —0.5 foot and +1.5 feet. Though 
the vertical distribution of Ruppia is thus very limited, its horizontal distribu- 
tion is quite wide. At its lower limit, near mean low water, Ruppia is found 
mixed with scattered Zostera, but it is also scattered abundantly over areas 
near the 1.5-foot level, where Zostera is entirely wanting, e. g., 1,300 to 1,600 
north along the east shore. Nowhere does the stand of Ruppia become as dense 
as the denser stands of Zostera, and, in fact, areas where the bottom is actually 
covered by Ruppia are small and rare. This is due not only to the relatively 
small number of plants, but also to their delicacy. 

The areas where Ruppia is most abundant are those with a soft bottom, 
bare of Ulva and usually protected from currents and waves. Such areas are 
those indicated on plate x11. They are found chiefly in the western and 
northern parts of the harbor, but there is another such habitat with abundant 
Ruppia along the eastern shore behind the Zostera belt. The horizontal distri- 
- bution of Ruppia is, in other words, limited to areas of quiet water and the fine, 
muddy soil formed in such areas. The vertical distribution of Ruppia, on the 
other hand, seems clearly determined by tide-levels. The lower limit of this 
species, as we have seen, is mean low water, or a few inches lower in exceptional 
cases, and the upper limit is at 1 foot, or more rarely at 1.5 feet, above mean low 
water. That is, the plant never occurs where constantly submerged, but rather 
on areas which are exposed for from 0 to 4 hours each day, depending on the 
magnitude of the tide. It seems clear that competition with other species 
can not be an important factor in keeping Ruppia out of soils at lower levels, 
since Ruppia does not occur on bottom below mean low water that is bare of 
Zostera and Ulva. The character of this bottom is apparently identical with 
that on which Ruppia is growing a foot or two higher up. There seems to be no 
difference in the conditions at these two levels, except in the relative duration 
of submergence and exposure. 

The upper limit of distribution of Ruppia may be determined in part perhaps 
by competitors, e. g., Spartina glabra, in the shade of which Ruppia occasionally 
grows at its upper level. It seems more probable that Ruppva does not flourish 
above the 1-foot or 1.5-foot level because unable to withstand the exposure to 
desiccation by air and sun at low water. This view is supported by the fact 
that Ruppia is most abundant in areas where it is kept wet by little rivulets 
that run over the mud at low tide, e. g., along the edge of the tide-stream at 


LITHOPHILOUS BENTHOS Lak 


2,000 north by 200 to 400 west. The same is true even if the water moisten- 
ing the plants at low tide is fresh water, e. g., at 1,300 to 1,600 north by 1,000 to 
1,075 east, or near the mouth of the creek at 200 north by 400 to 600 east. 


B. ATTACHED ALGAD OF THE HARBOR BOTTOM (THE “ LITHOPHILOUS 
BENTHOS ”). 

Under this head we include alge attached to stones, shells, or stakes below 
the 1.5-foot level, the “ Lithophilous Benthos” of Warming. Many specimens 
of these same species may be broken off and found drifting about the harbor 
entirely free of any support. Though 18 or 20 species of algee may be found on 
the bottom of the harbor, only 7 or 8 of these, including the Ulva and Entero- 
morpha clathrata mentioned above, occur in any considerable numbers. Even 
these are not at all abundant except in the Inlet, or, in the case of three or four 
species, along the streams entering the harbor. 

The species that have been found on the bottom at one time or another are: 
Beggiatoa mirabilis, Oscillatorva sp?, Cladophora (expansa?), Enteromorpha 
clathrata, HE. intestinalis, Ulva lactuca, Ascophyllum nodosum, Hctocarpus 
stliculosus var. amphibius Harv., Fucus vesiculosus, Pylaella littoralis, Scyto- 
siphon lomentarius, Agardhiella tenera, Callithamnion roseum, Ceramium 
rubrum, Chondria tenuissima, Chondrus crispus, Dasya elegans, Delesseria 
leprieuru, Gracilaria multipartita, Grinnellia americana, Hildenbrandia 
prototypus Nardo, Petrocelis cruenta, Polysiphoma variegata, Porphyra 
lacimata. 

In discussing the occurrence of these alge we may take up in some detail 
the distribution of the more abundant species in each class, and then note 
briefly the information that we have been able to gather concerning the 
occurrence of the rarer or occasional forms. 


SCHIZOPHYTA. 


Beggiatoa mirabilis occurs commonly on the surface of the black mud of the 
bottom, from below mean low water up into the present belt, and also, as we 
shall see, still further up, to the 6 or 7 foot level, in tide-pools, or in trickles 
of salt water at the edge of the estuarial marsh. Osctllatoria sp? was found 
only infrequently coating the surface of dead fronds of Fucus in the Inlet, at 
about mean low water. 


CHLOROPHYCE. 


Of the green algee enumerated above we have already noted the distribution 
of attached plants of Enteromorpha clathrata (p. 21) and Ulva (p.18). The 
only remaining species are Cladophora (expansa?), Enteromorpha intestinalis, 
and Ulothrix flacca. 

In April 1911 tufts of Cladophora (expansa?) 3 or 4 cm. long were found 
frequently along the Inlet near mean low water at 1,800 to 2,000 north. In 
September 1911 similar tufts were frequent in the creek, at 200 south, between 
the 1 and 2 foot levels. Considerable mats of it are found each summer tangled 
with Zostera and with other alge in the middle of the harbor bottom, where 
it also occasionally appears as an epiphyte on Zostera (plate vir). At this 
season it is much more abundant at higher levels, as we shall see later. 


28 THE RELATION OF PLANTS TO TIDE-LEVELS 


The large, simple, tubular fronds of Hnteromorpha intestinalis are likewise 
characteristic of higher levels, especially in the neighborhood of fresh-water 
streams. Along these streams, however, when they are large enough to reach 
to the low-tide mark as single streams, we sometimes find the Hnteromorpha 
accompanying them downward to within the limits of our zone. For example, 
at 20 south by 590 east, beside the main stream at the head of the harbor, at 
the 1.5-foot level, H. intestinalis is usually quite abundant and of good size, 
though neither as abundant nor as large as it is, at somewhat higher levels, a 
few feet south of this. A very interesting patch of this Hnteromorpha is that 
growing on the bottom near 1,440 north, on the east shore. At this point the 
overflow pipe from an artesian well penetrates the wall of the wharf at the 4-foot 
level. At low tide the water from this pipe falls to the bottom, which is at 
about the 1.5-foot level, where the water splashes down upon pebbles and 
stones, and then runs off over the bottom toward low-water level. A circle of 
the bottom 4 feet in diameter, round about the point where this stream strikes, 
is covered by hundreds of plants of Hnteromorpha intestinalis, from 5 to 20 
mm. in diameter and 2 or 3 dm. in length. A few dozen plants are found 
scattered along the stream running from this circle down over the bottom, but 
this latter area is dominated by Ascophyllum. Near another fresh-water outlet 
100 feet north of this we have a similar sparse sprinkling of this Hnteromorpha 
which does not dominate any appreciable area. The factors affecting the distri- 
bution of Enteromorpha intestinalis will be mentioned in discussing its distribu- 
tion at higher levels, where it is more abundant. 

Ulothriz flacca was found but sparingly below the 1.5-foot level in April 
1911, though it was everywhere abundant just above this. 


PHAOPHYCEA. 


Ascophyllum and Fucus: What has just been said of the relative abundance 
of Enteromorpha in this belt is true also of Ascophyllum and its relative Fucus, 
two genera which, because of their similarity of distribution, may be discussed 
together. ‘These alge attain their greatest abundance in the next higher belt 
of vegetation, in the harbor, from 1.5 to 6 feet. (See plate 1x.) The rela- 
tively few plants found below the 1.5-foot level grow on stones, chiefly along the 
channel to the Outer Harbor or along that from the Creek. Occasionally plants 
or clumps may be found on stones or sunken logs along the shores of the harbor. 
Near the middle of the harbor these alge are rarely found, and then they are 
attached to small pebbles or shells which they have evidently dragged with them 
from higher levels in the Inlet. 

From the distribution of Fucus and Ascophylium found in the Outer 
Harbor, it is evident that these plants may grow abundantly at, and somewhat 
below, low-water mark. It is therefore probable that the sparseness of these 
algee below the 1.5-foot level in the Inner Harbor is due in part to the absence 
below the bases of the wharves of any proper substratum for their attachment. 
The abundance of shifting Ulva is another important factor, for these sheets 
would be sure to bury the relatively slow-growing rockweeds before they could 
attain any considerable size. 

Ectocarpus siliculosus var. amphibius: This form has been found below 
the 1.5-foot level in only one locality, near a deep portion of the channel of the 


LITHOPHILOUS BENTHOS 29 


main stream, at 150 south by 780 east. Just upstream from this depression 
(160 south), the pebbly bottom slopes sharply down from a 1.5-foot level to 
—0.5 foot in the deepest parts of the depression, and then rises to about 
1 foot at the northern end of the hollow. In the bottom of the deepest part of 
this depression, and still more abundantly in the little rapids above it, the 
Ectocarpus grew in luxuriant tufts, with numerous gametangia, in the early 
summer of 1911. In late August of this same year it had practically disap- 
peared. The water flowing over this alga during 3 to 5 hours of each tide, or 
6 to 10 hours per day, is entirely fresh, while for the remainder of the tide the 
plants are surrounded by salt water. Moreover, the change from one to the 
other is quite rapid, which shows that the alga is capable of withstanding 
marked and sudden changes in the osmotic quality of the surrounding medium. 

Scytosiphon lomentarius: This alga occurs in the Outer Harbor all summer 
and unattached small tangles of it are found scattered over the bottom of the 
Inner Harbor at this same season. Only in early April 1911 did we find it 
attached in the Inner Harbor. At that time it was sprinkled in frequently 
among Ulva, Enteromorpha clathrata, Porphyra, and Pylaiella, on the stony 
bottom east of the channel of the Inlet, at 1,900 to 2,100 north and from mean 
low water up to the 1-foot level. These plants were 30 cm. long, about 1 mm. 
in diameter, and were fruiting. 

Pylaella littoralis: This densely branched filamentous brown alga has been 
found nearly every summer at one or more spots about the harbor. It is 
usually present, for example, in the deeper part of the Creek at 150 south at 
—0.5 to +1.5-foot levels. It was abundant in the Inlet in July 1912, but had 
largely disappeared by September. It is sometimes found also on the shady 
sides of piles or stones on the wharf of the Research Laboratory, chiefly, though 
not wholly, above 1.5 feet. In 1912 large tufts grew where splashed by fresh 
water at 150 north and 500 north on the west shore. In April 1911 this alga was 
probably the most abundant species about the harbor from mean low water 
up to 3 or 4 feet. At half tide its dense tufts could be seen everywhere, often 
as much as 1.5 dm. long. They were attached to pebbles, shells, stones, wood, 
and even tangled among the stalks of the Spartina glabra at its lower levels. 
All of these plants were either sterile or had chains of zoosporangia. On 
September 29, 1911, this same alga was found on pebbles in the deep part 
of the main stream at 150 south and in the rapids just above this at 200 south. 
In the plants collected at this time the only reproductive organs seen were 
gametangia, which had not been seen at all on plants collected in April or in 
midsummer. 

From what we have noted it is clear that Pylaiella, like Hctocarpus stliculosus, 
is capable of enduring the rapid change from salt to fresh water and the reverse 
which occurs in the main stream with each change of tide. It is also noteworthy 
that while this alga is very abundant and widely distributed about the harbor 
in April, it is represented in summer by only a few groups of plants in areas 
protected from high temperature and desiccation. The fact that the plants 
found in spring and early summer bore zoosporangia only, while those found in 
September bore only gametangia, suggests the probability that this alga really 
has a distinct seasonal alternation of a spore-bearing period with a gamete- 
bearing period. It may even prove to be an alternation of distinct asexual 


30 THE RELATION OF PLANTS TO TIDE-LEVELS 


and sexual generations, comparable with that of Dictyota and that of the red 
alge Polysiphonia and Griffithsia. (See Lewis, 1914.) 

The vertical distribution of Pylaiella thus far recorded extends from —6 
inches up to 5 or 6 feet. That is, it occurs both in areas where it is nearly 
always submerged and also, on shady spots along wharves, where it is exposed to 
the air from 8 to 9 hours each tide. It seems evident that this alga is not able 
to go higher on the wharves, nor, in most places, even as high as here recorded, 
because of the danger of desiccation during low tide. It perhaps does not grow 
on bottom below mean low water at the Inlet because of the swift current 
which runs over the bottom, sweeping along pebbles, shells, and dislodged 
alge. Why, if it can endure long submergence in fresh water, it does not push 
further up the fresh-water streams, it is not easy to understand, unless it be its 
inability to endure continuous submergence in fresh water. Pylatella would 
probably prove a good subject for experimental determination of the effect, on 
the distribution of alge, of such conditions as high temperature and exposure 
to fresh water and to dry air. 


THE RHODOPHYCE. 


Of the 13 species of this group of alge growing on the bottom of the harbor, 
the most important are Chondrus, Porphyra, and the incrusting alga Hilden- 
brandia. We will discuss these first, and then take up the remaining forms in 
alphabetical sequence. Plate 1x shows the distribution of the most frequent of 
the Rhodophycez about the harbor. 

Chondrus crispus is usually the most abundant red alga in the harbor, after 
the Ceramiums, Hildenbrandia, and perhaps Bostrychia. It occurs abundantly 
in the Inlet during the summer, chiefly on the pebbly bottom east of the 
channel, between 1 foot below and 1 foot above mean low water. In July 1911, 
for example, Chondrus was distributed over a strip varying from 10 to 40 or 
50 feet in width, and stretching from 1,700 to 2,000 north. The plants found 
here are from 0.5 dm. to 1 dm. in height, and form dense tufts of a reddish or 
brownish color. They are apparently quite as vigorous and fruit quite as 
freely as plants growing in open water in the Outer Harbor or in Long Island 
Sound. Two or three smaller plants were found at 1,600 north near mean low 
water. These were the southernmost plants ever recorded. Though this alga 
is one of the most constant in occurrence and distribution during each summer, 
it could not be found after careful search along the Inlet in April 1911. On 
September 28, 1911, this species was not seen, though searched for as carefully 
as possible, when the water was at the +1-foot level. 

Porphyra laciuniata: This is the only red alga found on the bottom of the 
harbor in April 1911. It was then nearly as abundant and widely distributed 
as Ulva, except that it was never found in or near fresh-water streams. ‘The 
Porphyra was then most abundant east of the channel to the Outer Harbor, 
from 1 foot below to 1.5 feet above mean low water. The individual plants at 
this point were often 2 to 3 dm. long, and about as broad. In other parts of 
the harbor, in April, the Porphyra is sprinkled about somewhat generally, 
though not abundantly, chiefly on wharves and wrecks between the 2-foot and 
the 4-foot levels. Hundreds of sheets of this alga, usually 1 to 2 dm. across, 
but sometimes larger, were seen in April among the stubble of the Spartina 
glabra along the west shore. Closer examination showed that the vast majority 


LITHOPHILOUS BENTHOS 31 


of these were detached, only a few dozens of them being attached to mussels. 
The only source that could at this time be discovered for such numbers of the 
plants of Porphyra was the dense colony of them in the Inlet. With so many 
detached plants about the harbor it is interesting to note that they do not settle 
on the bottom to cover large areas, as Ulva does. This is evidently because the 
Porphyra floats and is therefore cast up on the beach instead of settling. 
Porphyra is noticeably free from epiphytes, probably because of its lubricous 
surface. 

In the summer Porphyra is relatively rare in the Inner Harbor, though it is 
still abundant at various points in the Outer Harbor. The plants found in our 
area 1n summer are chiefly on the wharves, between 2 and 4 feet, and their 
distribution at these levels will be noted in discussing the rockweed association. 

The factors determining the distribution of Porphyra are not very clearly 
indicated by its occurrence in the area under observation. The limits noted in 
April and July, 2. e., —1 to +4 feet, are very nearly the limits of distribution of 
the plants found on the open shores of Long Island Sound. From the observa- 
tions here made it seems evident that cool water, stirred by waves or tidal 
currents, furnish the conditions favoring the growth of Porphyra. The upper 
limit seems to be determined by the time of exposure to the air, and the lower 
limit probably by the lack of light due to the turbidity of the water. It seems 
hardly probable that a delicate alga of a single layer of cells can be confined to 
levels above low tide, because of the need of exposure for aeration. 

Hildenbrandwa prototypus, an incrusting species, is more widely spread in 
summer than any other red alga of the Inner Harbor. It occurs on pebbles and 
stones at all levels from mean low water up to 6 or 6.5 feet and wherever there 
is a proper substratum. It grows both in pure salt water and in places where 
the plants may be overflowed for several hours at each tide by fresh water. For 
example, it is found abundantly on pebbles along the channel to the Outer 
Harbor from mean low water up to 1.5 or 2 feet, and on the shoals beside the 
Creek, at 470 east and 625 east at 1 to 2 feet, and, finally, it occurs within the 
present belt on stones of the wharf of the Research Laboratory, and of the 
wharves east of the Inlet at 2,200 north to 2,600 north. The distribution of 
this alga at higher levels and the factors determining its upper and lower limits 
will be discussed in describing the next higher belt of vegetation. 

The remaining ten species of Rhodophycee found on the bottom of the harbor 
are usually represented by few dozens or scores of individuals each. In fact, 
one or more of the species may be entirely wanting in some summers. Some 
of these ten species may develop in situ, on stakes or buoys, or on stones of the 
bottom. Others are rarely found fixed to a stable substratum. More often they 
are found drifting about over the bottom, being either entirely free or dragging 
about with them small pebbles or shells which hold the young plants in place, 
but which are too small to anchor securely the now full-grown plants. The ten 
species to which we have referred are: Agardhiella tenera, Callithammion 
roseum, Ceramium rubrum, Chondria tenuissima, Dasya elegans, Delesseria 
leprieurtt, Gracilaria multipartita, Grinnellia americana, Lomentaria uncinata, 
and Polysiphonia variegata. Of these alge Callithammion and Lomentaria have 
each been found during one season only, when a considerable number of plants 
of each were established in the Inlet, near 2,300 north by 1,175 east, at about 
mean low water. 


32 THE RELATION OF PLANTS TO TIDE-LEVELS 


Agardhtella is a coarse and rather cartilaginous species which is found 
abundantly in parts of the Outer Harbor and which often drifts into the Inner 
Harbor. It has not been found within our limits fixed to anything larger than 
small pebbles which are dragged about by the stiff, bushy plants. In some 
seasons dozens of these, and still larger numbers of entirely free plants, are 
tumbled about over the bottom, below the 1.5-foot level. 

Ceramium rubrum is abundant on Zostera in the Inner Harbor and is also 
found occasionally on pebbles or shells in the Inlet at 2,300 north by 1,000 to 
1,200 east at mean low water and below. Its relative, C. strictum, has not been 
found, except on Zostera. 

Chondria also has been recorded but once since our work began (in July 
1908), though it was often seen in earlier years in the same place,—2,200 to 
2,300 north, on the east side of the Inlet, at about the —1-foot level. In the 
one case recorded carefully the plants were about 1 dm. high, and all of them 
were tetrasporic. During the early years of this study Chondria was abundant 
in the Outer Harbor just outside the Inlet. At these times floating plants of 
Chondria were common in the Inner Harbor. The fixed plants outside the 
Inlet have disappeared almost completely during the last few years, and with 
them, of course, the free plants in the Inner Harbor. No cause has been 
discovered to which this disappearance of the Chondria, and of other red 
alge also, can be attributed with certainty. It seems probable that it is 
related to the sudden covering of large areas of the bottom by mussels which 
occurred in 1907. 

Perhaps the greater rarity of certain alge of the Inner Harbor in recent 
years is due to the greater distance over which the spores must come from 
areas outside it, where the plants are abundant and constantly present. It 
seems evident that fewer of the spores can reach the Inner Harbor from an 
_ area 2 or 3 miles away than from one 200 or 300 yards away, though as a matter 
of fact we have no certain evidence of the endurance of these spores or of their 
ability to remain afloat for so long a time. 

Delesseria is a smoky green, inconspicuous alga that has been found only 
once within the limits of the belt that we are discussing—at 1,750 north by 1,070 
east at the 1-foot level. It is more frequent at slightly higher levels, as we 
shall see later. 

Gracuaria is found in small numbers attached to pebbles and shells at levels 
between —2 and +1.5 feet on the bottom of the Inlet. It is sometimes also 
found being washed about over the bottom of the harbor, either entirely free or 
else dragging about with it the small pebble or shell on which it has grown. Both 
attached and free plants of Gracilaria have become less frequent of late years, 
probably for reasons identical with those suggested in speaking of Chondria. 

Grinnella is a broad, sheet-like alga which is quite frequent in the Outer 
Harbor. When our work began attached plants of it were abundant every 
summer in the shallow branch of the Outer Harbor directly north of the Inlet. © 
In 1906 three or four attached plants were found near 175 north by 625 east. 
These in all probability had been carried in by the tide and had dragged their 
small supports with them. Our records for 1907 show that half a dozen attached 
plants of this species were found in the Inlet between 2,200 and 2,400 north 
near mean low water. Plants which are entirely free are still found drifting 
over the bottom of the harbor, but while in earlier years these could be seen by 


LITHOPHILOUS BENTHOS oo 


the score, in 1909 and 1910 only a dozen or fifteen could be found in the whole 
harbor. Not half a dozen attached plants have been seen in the Inlet or Inner 
Harbor during the past two years. The filling up of the area of the Outer 
Harbor just north of the Inlet, which is correlated in some way with the abun- 
dance of mussels, has driven Grinnellia out of the area where it was formerly 
abundant, and from which the Inner Harbor could be readily supplied with 
spores and drifting plants. It is clear that in this, as in the case of the other 
red alge mentioned, we can not know with certainty the explanation of their 
distribution in the summer until we know more of their distribution and activi- 
ties during the other seasons of the year. 

Polysiphonia is abundant in some seasons on pebbles on the bottom of the 
Inlet from 2,000 to 2,600 north, between mean low water and —3 feet. Tetra- 
sporic plants are common in summer, while cystocarpic and antheridial ones are 
usually rare. In late September 1911 this alga was far more abundant than it 
has ever been in midsummer on the bottom of the east side of the Inlet from 
mean low water downward. In the region between 2,000 and 2,200 north, which 
was most carefully examined at this time, there were often 10 to 15 dense tufts 
to each square meter. All of these plants that were examined proved to be 
sexual, chiefly cystocarpic. In most summers a few drifting plants of Poly- 
siphonia are found in the Inner Harbor, some of them attached to small pebbles. 
In other summers these and the attached plants of the Inlet are practically 
wanting. When, therefore, we find in some succeeding summers a relatively 
large number of these plants in the Inlet, we are inclined to conclude for this 
species, as for the others mentioned above, that the new plants must come from 
spores brought in from the Outer Harbor, rather than from any perennating 
portions of plants of a former summer left in the Inner Harbor. The great 
abundance of this species in September 1911, however, suggests the possibility 
that its basal portions may be constantly present, but that its shoot is well- 
developed only in occasional summers, when conditions are unusually favorable 
at that season. 

The free or drifting plants of the red alge of the Inner Harbor that have 
been noted above may in some species remain in the living condition but a short 
time. Such, e. g., is usually the fate of the Ceramiums, Chondria, Dasya, and 
Polysiphonia. Other species, on the contrary, like the green alge Cladophora 
and Hnteromorpha, may persist indefinitely and even continue to develop. 
Thus, e. g., when Agardhiella, Gracilaria, and Grinnellia lodge on the bottom 
near low-water mark, they may continue to produce tetraspores or cystocarps 
for weeks after being torn loose from their substrata. In this way, of course, 
spores of alge not before growing in the harbor may be dispersed about it in 
considerable numbers. 


C. EPIPHYTIC ALGA ON ZOSTERA AND ULVA. 


About 7 or 8 species of the alge of the Inner Harbor are attached to other 
plants, chiefly to Zostera. In fact, it is the presence of Zostera, to serve as a 
substratum, that alone makes it possible for most of the epiphytic species to 
grow at all abundantly in the Inner Harbor. It is because of this importance 
of Zostera as a substratum that we have indicated its distribution on our topo- 
graphic map of the harbor. 

3 


34 THE RELATION OF PLANTS TO TIDE-LEVELS 


The species of alge which frequently occur as epiphytes on Zostera, on 
Ulva, or occasionally on other alge, are the following: Spirulina tenuwissuma, 
Cocconeis scutellum, Melosira borre, M. nummuloides, Navicula greviller, N. 
kennedyi, Synedra affinis, Cladophora (expansa?), Enteromorpha clathrata, 
Ceramium rubrum, and C. strictum. (See plates vir and Ix.) 

Among these epiphytic forms there is no general predominance of any one 
species, though because of their size and color the Ceramiwms may be more 
prominent. We may therefore discuss the species enumerated in alphabetical 
order within each class, beginning with the simplest. 


SCHIZOPHYCEZ. 


Spirulina tenuissima: This alga, as we shall see later, is widely spread from 
mean low water up to the 7-foot level, but it is in the present belt, as an 
epiphyte on Zostera, Ulva, and sometimes on Hnteromorpha clathrata, that it 
is most luxuriantly developed. On the Zostera this alga sometimes forms 
dense yellowish-green patches, sparkling with gas-bubbles and often many 
square decimeters in extent. For example, in 1910, patches of this sort 
were thickly sprinkled over hundreds of square meters of bottom from 1,300 
to 1,500 north by 950 to 1,050 east, covering one-third of the Zostera plants 
and matting scores of their leaves together. Similar, though usually smaller, 
patches of Sprrulina have been seen adhering to the large sheets of Ulva or on 
tangles of Hnteromorpha clathrata in the southeastern parts of the harbor. 
Still smaller patches occur occasionally on stakes or buoys in the middle of the 
harbor. These patches of Spirulina are 5 to 10 mm. thick and practically 
pure, showing but few other organisms within the mass, such as filaments of 
an Oscillatoria or of some other epiphyte of Zostera buried by the growth of 
the Spirulina. These dense growths of Spirulina are confined, in this harbor, 
to levels within a foot or less of mean low water. At higher levels, up to its 
upper limit at about 7 feet, Spirulina occurs sparingly mixed in mats or felts 
with numerous other Cyanophycesx, none of which seem to flourish near mean 
low water, where Spirulina does best. The lower limit of Spirulina in this 
harbor is about 1 foot below mean low water, and it is apparently conditioned 
by the presence in somewhat quiet water, which gets warm at low tide, of a 
substratum such as Zostera or Ulva over which it may spread. In its occupa- 
tion of substrata at higher levels it is restricted probably by the danger of 
desiccation, except in shaded areas or where it is protected by mats of other 
algw. Probably at higher levels also, in some localities, it is kept lower than 
usual because of lack of a suitable substratum. 


BACILLARIALES. 


The epiphytic Diatomee of the bottom of the harbor include the most abun- 
dant and widely distributed epiphytes of this belt. Cocconets scutellum, e. g., is 
found, often in great numbers, on nearly every plant growing in the Inner Har- 
bor. It grows not only on Zostera, but even more abundantly on Ulva and on 
both attached and free plants of other larger alge. It is often especially abun- 
dant on the epiphytic Ceramiums. The distribution of this diatom has not been 
studied in great detail, but it apparently occurs on all living substrata through- 
out the harbor, except near fresh water. In vertical distribution Cocconets is 
found from —2 feet to +1.5 feet. 


EPIPHYTIC ALGH ON ZOSTERA, ETC. Sys) 


Melosira borres and M. nummuloides: These diatoms, though less abundant, 
are even more widely distributed over the harbor-bottom than Cocconets, since 
they endure submergence, for several hours at least, in entirely fresh water. 
They are best developed, however, on the long leaves of Zostera or on stakes or 
buoys in the middle of the harbor. Here they form tufts of a rusty brown 
color from 2 or 3 to 25 or 30 mm. in diameter and from 4 or 5 to 25 or 30 mm. 
in length. The distribution of these tufts is somewhat more restricted than 
that of Zostera. They are present in considerable numbers only on the larger, 
denser Zostera near the center of the harbor. On outlying Zostera, as well as 
on Ulva, Enteromorpha, Pylaiella, and on several of the Floridexe of the 
bottom, Meloswra is found in single threads or clusters of few short filaments. 
Apparently all these Melosira tufts of the bottom and those along the Creek 
to 200 south are of the same species and are identical with those which occur 
mixed with Cyanophycese and Chlorophycee on marsh and beach at higher 
levels. The distribution of Melosira tufts is limited primarily by that of the 
plants on which it grows. It is evident, however, that though Melosira does not 
grow in the swiftest currents, it is most luxuriant where there is a considerable 
movement of the water, e. g., at the sides of the deeper channel leading from the 
Inlet toward the Creek and near the tide-stream entering the deep hole from 
the northwest. The abundance of Melosira on the Zostera, just aside from the 
swiftest current, where the Inlet opens into the Outer Harbor, confirms the 
conclusion that frequent change of the surrounding water is distinctly advan- 
tageous for this diatom. 

Navicula grevillei and N. kennedyi: These species have much the same dis- 
tribution as Melosira in the middle of the harbor, and are even more abundant 
and more luxuriant than Melosvra on the denser Zostera. The tufts of these 
Naviculas are distinguishable from those of Melosira by the somewhat lighter 
color, the slippery feel, and the abundant branching, as well as by the iridescent 
character of the gelatinous matrix in which the frustules are embedded. 

Synedra affinis: 'This is another diatom which is widely distributed on many 
hosts. It was especially abundant on Pylaiella in the Inlet on April 8, 1911, 
and on Pylatella and Enteromorpha intestinalis, in the Creek at 200 south in 
September 1911. On many branches of the Pylavella these diatoms stand out so 
thickly as to make these branches look lke diminutive chenille cords. 

There are of course other epiphytic diatoms (see list on p. 161), but those 
mentioned are the most abundant and widespread in distribution. 


CHLOROPHYCE. 


The only important epiphytic Chlorophycee are Chetomorpha erea forma 
linum, Cladophora (expansa?), and Enteromorpha clathrata. 

Chetomorpha erea: Though this is originally epiphytic, it is found most 
frequently lying on the Ulva or tangled with Zostera, Cladophora, or Entero- 
morpha on the bottom, near the middle of the harbor. What is apparently the 
same species is found at higher levels among the Spartina glabra. 

Cladophora (expansa?): This is a species which is rather frequent in little 
tufts attached to Zostera near the deep hole, though far less abundant than its 
fellow-epiphytes Hnteromorpha clathrata and the two Ceramwms. The tufts 
of Cladophora are 2 or 3 cm. long and are made up of repeatedly branched and. 
densely interwoven filaments. 


36 THE RELATION OF PLANTS TO TIDE-LEVELS 


Enteromorpha clathrata: The occurrence of this species as an epiphyte we 
have already mentioned when referring to the long, streaming tufts of it on the 
Zostera as the source of the loose mats of this alga that drift over the bottom. 
We may here emphasize the fact that it is very abundant as an epiphyte. Often 
a dozen large tufts of it may grow on a single leaf-cluster of Zostera, and the 
filaments may attain a length of several decimeters before being set free, which 
usually occurs by the rupture of the supporting leaf. H. clathrata also has a 
wide distribution. It is the only noticeable epiphyte on the outlying clumps 
of Zostera, except a few tufts of Melosira. 


RHODOPHYCE. 


As indicated in our enumeration of species, only two epiphytic red alge © 
have been found in the harbor, and both belong to the genus Ceramium. 
Though Polysiphonia occurs as an epiphyte on Zostera in other Long Island 
waters, mature plants of this species never have this habit in our harbor. 
Melobesia, another epiphyte found in more saline waters about Long Island, 
does not occur here at all. 

Ceramium rubrum: This alga‘ forms dense tufts, 5 to 10 cm. long, on the 
leaves of Zostera. Dozens or scores of these large tufts may sometimes be seen 
on each square meter of the Zostera, and in such areas this Ceramium is the 
most prominent epiphyte. This alga is most abundant just aside from the 
swiftest current along the Inlet, about the deep hole, and beside the tide- 
stream entering the latter from the northwest (plate Ix). Evidently this red 
alga, like Melosira, flourishes best in moving water. In fact, the Ceramiwm 
fails to accompany the Zostera to the limit of its distribution, the outer or upper 
third of the Zostera being bare of the alga. Some of the plants of this Ceramium 
found in July and August bore tetraspores and others cystocarps or antheridia. 

Ceramium strictum: This is the only red alga of the Inner Harbor which has 
. been found here solely as an epiphyte. It is somewhat smaller in size and 
brighter in color than C. rubrum. The distribution of C. strictum is in general 
similar to that of C. rubrum, but it is evidently still more closely confined to the 
Zostera immediately surrounding the deep hole and the tide-stream flowing 
into it from the northwest. } 

So far as has been determined from a study of the epiphytic alge of the 
harbor bottom, a study which has been concerned especially with the Ceramiums, 
these alge are found at levels where they are submerged at all but the lowest 
tides. They evidently will not endure long exposure to dry air. The absence 
of the Ceramiums from the Zostera growing in the area from 500 to 700 north 
by 200 to 600 east indicates that these alge can not endure submergence in the 
brackish, and for part of the time actually fresh, water which flows from the 
Creek at low tide. 


3. THE MID-LITTORAL BELT (1.5 TO 6.5 FEET). 


As one looks about the harbor at low tide the whole natural shore for some 
distance below high-water level is seen to be occupied by a very clearly marked — 
belt of vegetation of quite uniform character. Closer examination shows that 
the sole conspicuous plant of this green belt is the salt reed-grass Spartina 
glabra var. alterniflora, and that it really occupies the middle portion of the 
strip of muddy shore between the two tide-marks. In fact, except where 


PLATE Ill 





with 


00 North X 500 East, 


2 


’ 


2 


near 


b) 


a 


Ge 


losus spira 


va glab 


Spartir 
Cus VES 


A. Lower Edge of Zone of 


1s. 


1 


wu 


Fu 





ith Upper Part of Belt of Fucus and 


yllaam 


U 


WwW 


ide, 
Sc 


00 North on East S 


aUet.6 


td 


B. Wall 


D 


oph 


A 


% 





PEATE IV 





A. South Shore of Spit looking Eastward from 100 West, showing Upper Margin 
of Spartina glabra alternifiora (at right), Sueda (in center middle distance), 
and at left Ammophila, Solidago, and Ailanthus. The tide stakes are at 
7, 8, 9 and 10 feet respectively. 





B. Portion of East Shore just South of Mill (400 to 500 North), showing Spartina 
glabra alternifora and Scirpus americanus (left foreground). Sambucus and 
Ailanthus (center background), Solidago sempervirens and Iris versicolor 
(right foreground and middle distance). 


. 


= : 
> 1 
-_ 


7 





MID-LITTORAL BELT at 


local conditions of soil-moisture or shade are unusual, this grass is confined 
to levels between 1.5 and 6.5 feet. On the mud with the Spartina are found 
one other seed plant, Lilwopsis, and numerous alge, mostly small and incon- 
spicuous, except where matted together in numbers. 

If the observer now turns to the portion of the harbor’s edge bounded by 
wharves, he finds the stone walls and piles between tide-marks occupied by a 
belt of brown rockweed. Closer examination of these areas shows that they also 
are generally confined between the 1.5 and 6.5-foot levels, and that, though 
numerous other alge may be found here, the areas are dominated by the rock- 
weeds Ascophyllum and Fucus. 

These two types of vegetation, found between 1.5 and 6.5, we may designate as 
the Mid-littoral Marsh and the Mid-littoral Rockweed Association respectively. 
Together they bound practically the whole circumference of the harbor. The 
only breaks in this distinct belt or zone are the. stream-beds and two or three 
short stretches of artificial gravel beach. 


A. THE MID-LITTORAL MARSH. 


This belt, as has just been indicated, is a Spartinetum, dominated com- 
pletely in most areas by Spartina glabra. It evidently corresponds in many 
respects to the “ salt-reed swamp ” of Warming (1909, p. 223). There are two 
striking features of this marsh at Cold Spring Harbor. In the first place, there 
is no admixture of other seed plants save half a dozen small patches of Lileop- 
sis and a few scattered migrants from the next higher belt, which wanderers, 
except near fresh-water streams, never get more than a few inches below the 
6-foot level.* In the second place, this Spartina lies exactly in the middle of the 
“littoral region,” if, with Kjellman (187%, p. 57) or Oltmanns (1905, p. 167), 
we define this region as that lying between the two tide-marks. Kjellman 
chooses the extreme upper and lower tide-marks as the boundaries of this littoral 
zone, on the west coast of Nova Zembla. But at the place where he worked the 
range of tides is small and the maximum range differs but little from the mean 
range. In the harbor we are dealing with the mean tide-limits have been chosen 
as boundaries for the littoral belt because the extreme range of tides is much 
greater than the mean, and because this choice gives us a belt characterized by 
distinct vegetational types. 

At Cold Spring Harbor, where mean high water is about 8 feet above mean 
low water, and where the Spartinetum lies between 1.5 and 6.5 feet above mean 
low water, this association seems very aptly named the Mid-littoral Marsh. 
Moreover, from observations made elsewhere on Long Island and on Casco Bay, 
Maine, we are led to believe that the salt reed-grass along our whole North 
Atlantic coast will be found to be located just about midway between the mean 
tide-marks. We believe the name here used may be found generally applicable 
and clearly descriptive, for this Spartina association, wherever its vertical 
distribution is accurately determined. 

In our detailed discussion of the vegetation of the Mid-lttoral Marsh we will 
first consider the distribution of the Spartina and the other seed plants that 
are associated with it in its upper portions, and then take up the distribution 
of the algal felts or tangles and more scattered alge which form “ subordinate 
communities ” on the bottom between these seed plants. 


* Scirpus nanus also has been seen below the 6-foot level in a few places on the 
Marsh. 


38 THE RELATION OF PLANTS TO TIDE-LEVELS 


1. THE SPARTINA GLABRA ASSOCIATION. 


In discussing the character and distribution of this association it will be 
best, because of the differences in their nature, to take up the north shore 
separately from the east, west, and south shores. Nowhere else about the 
harbor does the Spartina association assume such prominence as along the south 
side of the Spit, which stretches across the north end of the Inner Harbor. 
We may therefore legitimately regard this as the highest development of the 
Spartina association and discuss in this connection not merely the distribution 
of the Spartina in this particular area, but also the general vegetative and 
reproductive characters always shown by this grass wherever found. The area 
occupied by Spartina on the Spit is greater than the sum of all the other 
Spartina areas of the harbor. 

Starting at the northwest corner of the harbor, we find that there is a pocket 
in the shore about 200 feet in diameter quite filled with Spartina, except for a 
few tide-pools and a fresh-water stream from a ram. From this region east- 
ward to 200 east the border of Spartina is 50 to 100 feet wide (plate vir 4). 
It then suddenly broadens out until, from 500 to 900 east, the Spartina stretches 
out 600 or 800 feet southward from the shore of the Spit proper (plate 1). This 
broad band of 8. glabra along the eastern third of the Spit serves, we shall see, as 
a protecting barrier of great importance to the plants of the upper levels of the 
beach, above 6.5 feet. 

From 800 west to 200 east the lowermost stands of Spartina are on bottom at 
from 2 feet to 2.5 or 3 feet above mean low water. Eastward from here the 
lowest or southernmost boundary of the Spartina corresponds pretty closely with 
the 1.5-foot tide-line or contour, as it does elsewhere about the harbor (see 
plate 1). It is noteworthy that though the lower border of this marsh is very 
irregular as far as 600 east, from there eastward and northward it is quite 
regular. This latter fact is probably related in some way to the presence of the 
‘strong tidal-currents through the Inlet. We shall have occasion to recur to 
this later. The level of the soil bearing most of the Spartina for 30 or 40 feet 
inward from this southern margin of the Marsh lies between the 2 and 3 foot 
levels. The upper limit of Spartina throughout this band is near the 6.5-foot 
level (plate x). Only in a few places does it fall to, or slightly below, the 6-foot 
level, as on hard gravel or on shifting sandy bottom at 2,800 north by 900 east. 
In the northwest corner of the harbor, 900 to 1,000 west, rather thickly scattered 
Spartina may grow as high up as the 7.5-foot tide-line, though the dense, pure 
stand ends here as elsewhere at about 6.5 feet. The cause for a local rise in 
the upper limit at this point is perhaps to be found in the extreme flatness of 
the shore here, which causes poor drainage, such as we shall find on the marsh at 
the south end of the harbor. Possibly the wet soil here is due to the presence of 
fresh water in the subsoil, though no adequate evidence of this has been found. 
We do not find here Scirpus americanus or S. robustus, which are commonly 
found in soil containing fresh water at these levels. 

The substratum upon which most of the Spartina glabra of this south shore 
of the Spit is growing is a more or less firm, peat-like muck. At the eastern end 
of the Spit, at both upper and lower limits, Spartina is found on a sandy 
bottom. The muck referred to may, at the upper end of the Spartina belt, be 
but a few centimeters in depth, while at the middle or lower portion of this 
belt there may be 0.5 meter or more of this muck, overlying the hard sand 


+{OFT. 


‘ 
A 
GRAVEL Ve 


SPARTINA GLABRA ASSOCIATION 39 


or gravel. For example, a series of soundings through the mud of the bottom, 
at different levels, along the main north-and-south axis, beginning at 2,700 
north, showed the following thicknesses of soft mud above the hard bottom: 
at the 6.5-foot level 5 cm. of mud; at the 6-foot level, 15 cm.; at the 5-foot 
level, 38 cm.; at the 4.5-foot level, 40 cm.; at the 4-foot level, 43 cm.; at the 
3-foot level, 70 cm. ; at 2.5-foot level, 66 cm.; at the 2-foot level, 36 cm.; finally, 
at the 1-foot level there was a thickness of but 30 cm. of mud above the firm 
subsoil. The thickness of the Spartina-bearing mud can be seen in the cross- 
section of this part of the shore of the harbor shown in figure 1. 

The rhizomes of the Spartina branch freely and run along more or less 
horizontally at about 1 to 1.5 dm. below the surface of the mud. The rhizomes 
are about 7 to 9 mm. in diameter and the living portion is about 2 or 3 dm. 
long. It consists of several or of many internodes, and may branch several 
times in its length. The terminal bud of the main axis maintains its horizontal 
position, while the lateral offshoots turn upward and give rise to the aerial 
shoots. From the base of each of these shoots a new rhizome puts out, in the sea- 
son after the leafy shoot is unfolded. By the network of interwoven rhizomes 


{ AMMOPHILA 
OISTICHLIS | CAKILE 
SPART. PATENS | 74 LIMONIUM 
SALICORNIA j | |SALSOLA 
SUAEDA A SOLIDAGO 
i 


ENTERO MORPHA\ 
7 : Spi 
ala ri D spaRTINA GLABRA ee eee ae 
cha Os a AND ALGAE 7, 0h ft \ 
¥ x. / ye 


TIDE STREAM, gp EN 
’ ' ~ 


Fic. 1.—North to south vertical section, at 0 east, of the Spit and adjoining portion 
of bottom, showing the depth of peat or mud overlying the gravel substratum, and 
the more important plants that dominate each level. Horizontal scale 1 = 3,000. 
Vertical scale 1 = 300. 


thus formed, which is in some places 4 or 5 layers thick, and by the roots which 
penetrate to still greater depths, the soft mud is firmly bound together for 2 or 3 
dm. below the surface. 

The aerial shoots push up above this substratum in the summer to a height 
varying from 1 to 2 meters, and sometimes have a diameter of 1.5 or 2 cm. at the 
base. In the denser stands of this grass there may be from 300 to 600 stalks per 
square meter. Hach aerial shoot may bear 1 or rarely 2 bladeless leaves at its 
base and 6 to 12 complete leaves toward the top. The size and general vigor of 
the plants differ greatly with the level of the soil in which they are rooted, and is 


usually greatest on bottom between the 3-foot and 6-foot levels. For example, 


Spartina growing on mud between the 3 and 3.5 foot levels, near 2,200 north 
by 600 east, is 15 to 20 dm. high, while other plants nearby, on soil at the 1.5 or 
2 foot levels, reach only 8 or 10 dm. in height. 

The flowers of some of the Spartina plants begin to open in the latter half 
of July, nearly 3 months after the shoots push up from the stubble in late April, 
but it is only the more vigorous plants, e. g., those on bottom between the 3 and 6 
foot levels, that begin to bloom as early as this. The smaller plants at lower and 





40 THE RELATION OF PLANTS TO TIDE-LEVELS 


higher levels do not begin to bloom until much later than this, often in late 
August or even in early September. Apparently seeds are set rather freely on 
the stronger plants and a considerable crop of seedlings might be expected. 
As a matter of fact, seedlings are not very abundant, because, it seems, wnoc- 
cupied soil of the proper character and at the proper levels is not frequent. 
The seedlings that have been found in midsummer were growing on bottom just 
above the 1.5-foot level, that had evidently been disturbed by clam diggers (100 
north by 475 east), or by water-currents (2,000 north by 1,100 east and at mouths 
of Creek and rivulets), just at the time that the seeds were being dispersed by the 
water. This stirring of the bottom formed pits and furrows in which the seeds 
were readily buried.* Seedlings found at the first station mentioned, on July 1, 
1911, presumably from seeds ripened in 1910, were from 1 to 2 dm. high, had 
leaves, and a well-developed root-system, though the glumes were still attached. 
Our search for seedlings more than a year old was unsuccessful. All medium- 
sized plants examined proved to be young shoots at the tips of long runners from 
mature rhizomes. 

It is evident that the usual means of propagation and spreading to con- 
tiguous areas is by the longer branches of the rhizome. In this way the 
borders of a clump of Spartina may be spread 4 or 5 dm. in a year, but it 
probably takes several years to produce, on such an added area, a dense stand, 
such as was mentioned above, of 300 to 600 stalks to the square meter. Another 
means of spreading to more distant parts of the harbor is through transporta- 
tion of whole tufts or mats of rhizomes by the ice. The stubble, which is tough 
in early winter, may apparently be frozen in blocks of ice at low tide, and when 
these blocks float up with the rising tide whole clumps of Spartina, with 2 or 3 
dm. thickness of mud tangled among its rhizomes, may be lifted and carried to 
other parts of the harbor. It is only when these clumps happen to be dropped 
on bottom at or above the 1.5-foot level that they persist for more than one 
season. It might be assumed that clumps lodging below the 1.5-foot level dis- 
appear in winter through the agency of ice, but, as a matter of fact, they do not 
thrive even for one growing season. Dead clumps of turf are often seen on the 
bottom, showing where living turfs have been dropped. Harly each summer 
one or more considerable clumps of the grass are found growing in new loca- 
tions, sometimes near the very middle of the harbor. The death of this grass at 
levels below 1 foot or even 1.5 feet is probably due to its inability to withstand so 
long a submergence as it is there subjected to. Experimental work is under way 
by which we hope to determine whether this is the real explanation. 

A very interesting feature of the distribution of 9. glabra at its lower limit is 
the suddenness with which it ceases to spread downward over the bottom when 
the 1.5-foot level is reached (plate 1114). The soil may be quite densely covered 
with Spartina even at the lower limit of its distribution, and the presence of its 
rhizomes gives the bottom sufficient firmness to enable it to support the weight 
of a person walking over it. The bottom just beyond that bearing Spartina 
drops abruptly to a level 6 or 8 inches lower. This lower bottom is usually very 
soft for a depth of several decimeters. About tide-pools and the little inlets 
making into the mid-littoral marsh, near 2,500 north by 200 east, we find this 
same sudden drop to lower and softer bottom. It is difficult to see why the 





* Once only (at 100 north by 1,000 east) were seedlings of S. glabra found growing 
in the peaty mud among the parent plants near the 6-foot level. 


PLATE (V; 


1000 E 

















IOOOE 





600 400 200 W. 







MAP OF SYMBOLS 


(BESIDES THOSE USED IN TABLE F) N 


ls H E S By db Ao = Asparagus officinalis | 


Sy = Digitaria (serotina, 













































































































































COLD SPRING HARBOR er agit 
u= Elymus virginicus hf Candee 
LONG ISLAND, N.Y Se alae la 8 rani 100s eae 
y aa Se = Triplasis purpurea 
SHOWING DISTRIBUTION OF PLANTS GROWING VB = Verbascum Blattaria : 6 y ~ 
’ | Ur ; : : Z IS M4 y 4277/3 
ON THE SPIT IN AUGUST 1913. OEE INE Seah pe” ae NG IP 0s oe one 
Q = Atripler arenaria GTAP PTL 4 OF. 7 LE LOG oe LAPoPO KS i 
By Haran H. Yorx = Atr?, CHE, S4,0n77 S85 SH AONI9 4 
= 5 O = Atriplex patula hastata 24) 1 as 
=M ictUlata CO pe 
2800N}-—— desea page Pe 2800 N 
® = Salicornia ambigua 
Scale 1:1000 Obra Orsos ; ac 
) 50 100 150 200 250Feet $= Spartene patens Le COGS OO: HEX: Sioa HS 
Se Pekan . ; ALLO CSPI IRL? Sg as aR ee <Sd— - “Sk 
= Upper limit, Spartina glabra alterniflora ae faye J y 46 as i ma, Fasghae 0 Soyo her Ashok Ss 
| ii= Suaeda maritima ait * §a Sa’ Base eS 3 yo Se aay 5c EvSa Sy Sk Sk sk j 
=Salicornia europaea Ee ask ~ Sk 
ee LIES 
“0 rw aicee ‘5: 
EU, sqseSe Se 5 
“Svsare Se Coane - 
ce 
2600N 
( Be gE ee 5 
ot She SRK LT Cog NG 8 
Ss rr LES OPS PED IEE T GS bbe 
LLL SL Ma 
Z AE SA IRS eae POT, 
r TEE BE Fe f 7 
S \ pa! hee 
SSAA 
SQQ9 
shed E SS SSNS 
2400N 














1O00E 


SPARTINA GLABRA ASSOCIATION 41 


rhizomes of the reed-grass do not rather quickly occupy these areas, which 
might then soon be built up by the deposit of the silt brought in abundantly by 
the tide. The only plausible explanation of the persistent absence of Spartina 
below the 1.5-foot level is that the conditions encountered by the rhizomes or 
shoots at these lower levels are unendurable. Just what the ultimate injurious 
factors in these conditions may be we shall suggest later, in our general discus- 
sion of the factors affecting the whole distribution of Spartina glabra. 

Practically the whole of the area south of the Spit, shown within the finely 
zigzag line on the chart, and up to just beyond the 6-foot contour, is covered 
continuously and year after year with Spartina glabra. The only considerable 
tide-pools and larger notches of bare mud along the margin are shown on our 
map. Moreover, aside from the relatively inconspicuous alge matted about 
the stalks of the Spartina, where it is less dense in growth, no other plants 
participate with Spartina in occupying the soil. Absolutely no other established 
seed plants are found in this area until we reach the 6-foot level, where we 
begin to encounter inwandering angiosperms from the next higher belt of 
vegetation. A description of the species competing with Spartina at its upper 
limit, and also of the local distribution of Spartina itself at these higher 
levels, may be left until we take up the discussion of the next higher belt of 
vegetation. 

On the east side of the harbor, because of the wharves, we find only one rather 
short strip of well-developed Spartina association. This one piece of natural 
shore on the east side extends from 100 south to 500 north, and the Spartina 
association is developed in a very interesting way here, evidently because of the 
presence of an abundance of fresh water along this shore. North of the mill, 
from 600 to 800 north, between 975 and 1,175 north, near 1,400 north, 1,650 
north, 2,150 north, and 2,400 north, there are found strips of Spartina from 
1 to 10 meters in width growing at 2 to 4 feet above mean low water, along the 
base of the wall of the wharves. These strips are covered by typical Spartina 
alone, except for the alge usually associated with it, and will therefore not be 
- considered further. 

The Spartina belt between 200 north and 500 north forms a nearly con- 
tinuous fringe, 10 to 30 meters wide, occupying the eastern shore between the 
1.5 and 6.5 foot levels, though these limits vary slightly. From 200 north to 
100 south the fringe of Spartina is only 10 to 15 meters wide, and is broken 
through at half a dozen points by fresh-water rivulets. The stand of Spartina 
shows much the same density and other characters here as on the Spit. The 
extreme lower plants, from 200 north to 500 north, are on soil at the 1.5-foot 
level, and are small and late in flowering. South of this the lower limit for 
this species moves upward till from 0 to 100 south the lowermost plants are 
often at 3 feet or even 4 or 4.5 feet above mean low water. The salt reed-grass 
is evidently kept up on high levels here by the high level of the neighboring 
tide-stream at low water. If, for example, at 100 south, Spartina were to 
grow at the 3-foot level, it must needs grow in the bed of the tide-stream, 
where the rhizomes would not only be submerged most of the time during low 
tide, but would also have to push through a firm gravelly soil. The eastern bank 
of the tide-stream all along here usually drops from a level that varies from 3 
to 6 feet above mean low water, downward abruptly for 1, 2, or 3 feet to the 
stream-bed, and Spartina is confined to the top of the bank, or to undermined 


42 THE RELATION OF PLANTS TO TIDE-LEVELS 


portions of the Spartina turf that are hanging down into the stream. Along 
all the fresh-water rivulets shown on the map between 0 and 200 north the 
Spartina keeps upon the firm peat at the side, 6 or 8 inches above the constantly 
flooded gravel bottom of the rivulet. The rhizomes and roots must often reach 
down nearly to the fresh-water level. Only at one place about the harbor has 
S. glabra been found growing where its rhizomes are constantly immersed. 
This was in a pool of 10 feet in diameter filled by fresh water falling from the 
flume south of the mill (plate tvs). The surface of this pool was at the 5-foot 
level, and the Spartina is rooted in soil some inches below this, so that its roots 
and rhizomes were surrounded by fresh water for 6 or 7 hours each tide. In 
1910 the water was shut off from this millrace and it is now dry. The only 
seed plant growing in the beds of these fresh-water rivulets is Lileopsts lineata, 
which we have already mentioned as the only other seed plant characteristic 
of the Spartina belt. In the bed of one of these rivulets near 150 north, 
between the 4 and 6 foot levels, hundreds of these tiny plants with their bladeless 
leaves lie appressed to the gravel, while the cold fresh water runs over them 
for 6 to 9 hours each tide. 

The steepness of the shore, the character of the soil, and the abundance of 
the supply of fresh water are very different on different parts of this eastern 
side of the harbor. In evident consequence of this we find that the upper 
limits reached by Spartina glabra, and by the other plants with which it comes 
into competition on the upper portions of the mid-littoral belt, are much more 
variable than on the Spit, where we found a very regular upper margin of the 
dense Spartina running along the 6.5-foot tide-line. For example, at 200 
north there is a rather well-drained bit of mid-littoral beach. In this region the 
pure dense growth of Spartina ceases at the 5.5-foot level. At the 6-foot level 
it becomes rather equally mixed with S. patens, which becomes dominant from 
_this level up to 7.5 feet. Only a few scattered small plants of S. glabra reach 
to the 6.5 and %-foot levels. At 350 north, where the east shore between 5 and 
7.5 feet is of coarse gravel, and supplied with very little fresh water trickling 
over the beach at low tide, the pure stand of S. glabra ends at 5.5 feet, where it 
becomes mixed with Scirpus americana and with still fewer plants of Spartina 
patens. Above the 6-foot level the latter becomes dominant and S. glabra is 
sprinkled more and more sparsely with it, and with Scirpus americanus, up to 
the 7-foot level. Above this the S. glabra is wanting altogether. 

From 400 to 500 north, where, in some places fresh water is trickling over 
the beach from above the 8-foot level, and in other places where it is seeping 
out of the gravel at lower levels, we find the dense S. glabra going up to the 
6.5-foot level, in places where the turfs are kept continually moist by fresh 
water running constantly about them. Here, as elsewhere, it does not grow at 
all where fresh water is running directly over the soil in which its rhizomes are 
embedded. Usually this is evidently because the fresh-water rivulet cuts away 
the peaty soil down to the underlying gravel in forming its little channel. The 
rhizomes, except in the pool below the mill-wheel, are always in soil high enough 
above the beds of these rivulets so that the soil-water always remains more or 
less saline even at low tide. It is probable also that the water constantly 
running over the beach may keep the air about the leaves of the short Spartina 
of the upper levels more than usually moist during low tide and thus, by 
reducing transpiration, enable it to creep a little higher up the beach. Along 


SPARTINA GLABRA ASSOCIATION 43 


most of this shore from 350 to 500 north the Spartina is not replaced at 
its upper margin by a dense growth of Spartina patens, as it generally is 
further south, but instead by a relatively bare gravelly beach merely sprinkled 
with plants, which are, however, of considerable variety. Thus, for example, 
plants of Solidago sempervirens are encountered at 6 feet, and a few seedlings 
even at 5 feet. Salicornia europea is found from the 5-foot to the 6-foot level. 
Atriplex patula hastata occurs at 5.5 feet, out of reach of fresh water. Scirpus 
americanus follows the fresh water down to 6 feet. Triglochin maritima goes 
down to 6 feet. Plantago decipiens first appears at 6.25 feet. Scirpus nanus 
forms dense turfs on mud out of reach of flowing fresh water at the 6.25 to 6.75 
foot levels. These plants apparently are able to invade the Spartina belt 
because the presence of fresh water, either by its direct action on the roots or 
by washing away the peat from above the gravel, makes it difficult or impossible 
for the Spartina to compete with the invaders on these areas. Most of these 
competitors, it should be noted, are established on the bare gravelly areas. 
Only the Scirpus americanus and S. nanus and some plants of Salicornia and 
Plantago are found on mud, the favorite soil of the Spartina. 

The western shore of the harbor is not so completely occupied by wharves as 
is the eastern, and it therefore bears much larger strips of Spartina glabra. 
From 550 to 1,050 north the fringe of Spartina varies from 12 to 20 meters in 
width and has quite regular upper and lower borders, the former being through- 
out very close to the 6.5-foot level, and the latter running along between 
the 1.5 and 2 foot levels. From 1,220 to 2,400 north the Spartina belt is much 
more irregular in distribution, probably because of local differences in the 
amount of shade and of fresh water present along this part of the shore. 
The width of the Spartina association varies from 5 or 6 to 30 or 40 meters, as 
may be seen on the chart, and it is interrupted only by the fresh-water streamlets 
and by a small wharf at 2,200 north. The lower margin of the stand of 
Spartina runs along at or just above the 1.5-foot level as far as 2,000 north, 
but in the extreme northwest corner of the harbor retreats to the 2.5 or even 
_ to the 3-foot level. The upper margin runs near the 6.5-foot contour, but in 
a few wet or shady areas fairly dense growths of Spartina have been found at 
? or 7.5 feet, and scattered plants at even the 8-foot level. 

The stand of Spartina along the west shore, except where it extends above 
the 6.5-foot level, is pure and generally very dense. There are often 500 or 
600 stalks per square meter. The plants vary from a height of 6 to 9 dm. in 
the upper parts of the belt to a height of 18 or 20 in the middle and from 6 to 
10 or 12 near the lower margin. The largest plants seen were 23 dm. high. 
These were growing in a layer of mud 1 dm. thick, overlying a sandy subsoil at 
the 3.25-foot tide-level. On most portions of the west shore the bottom rises 
with a very sharp slope from about the 4-foot to about the 6-foot level. The 
plants of Spartina are all within a strip a few meters in horizontal width. 
Those plants growing on levels below 4 feet are rather short, being from 8 to 
10 or 12 dm. high, while those growing between 5 and 6 feet are commonly 15 
to 18 dm. high. The difference in level of bottom, combined with difference of 
size of plants, makes the Spartina appear, to one rowing along this shore when 
the tide is nearly low, as though it grew from two terraces of 3 or 4 feet 
difference in level. At half tide the outer edge of the Spartina on the upper 
terrace rises so abruptly above the water that it appears to be the outer margin 
of the whole Spartina belt. 


44 THE RELATION OF PLANTS TO TIDE-LEVELS 


The blooming of the Spartina on the west shore shows the same features that 
have been noted in plants growing on the Spit. 

The largest areas within the boundaries of this part of the Spartina belt that 
are not covered more or less densely by this grass are the beds of the fresh-water 
streams entering the harbor on the west side. The more important of these are 
indicated on the map. Wherever any considerable rivulet runs down over the 
beach it cuts the Spartina belt clear across by washing off the peaty mud down 
to the underlying gravel. ‘The smaller of these channels, running across the 
beach, are but a decimeter or two in width, while the larger ones may bare the 
gravel for a width of 1, 2, or rarely 3 meters. On the edges of these channels 
the firm mud, on which the Sparta grows, stands at a level of 2 to 4 dm. above 
the bed of the rivulet. On the edges of these steep banks the Spartina stops 
abruptly, just as we have seen it do along the tide-stream in the southeast 
corner of the harbor. This is also much the way the stand of Spartina ends 
about the reentrant notches along its ragged outer border. Such notches are 
found especially along the west shore. On the projecting points of the dissected 
edge of the Spartina area, however, the firm peat slopes off gradually to the 
soft mud of the harbor bottom, and here the Spartina does not stop abruptly, 
but thins out rather gradually. Much of the raggedness of the outer edge of the 
Spartina belt is probably due to the burrowing through the substratum of the 
muskrat (Fiber zibethicus). 

The stand of Spartina along the west shore is practically pure up to the 
6-foot level. The only other plants commonly occupying the bottom between 
these levels are the gelatinous or felted green and blue-green alge, with 
occasional tufts of Ascophyllum and tangles of Pucus. On two small areas close 
together at 1,845 north and 1,860 north a few hundred plants of Lile@opsis were 
found between the 6 and 6.5 foot levels (plates x1r and xx11). As in the case of 

the LInleopsis found in the southeast corner of the harbor, these also seem to be 
- associated with fresh water. In these particular areas on the west shore there is 
no fresh water running over the surface, but if a stake is pushed into the soft, 
spongy mud and withdrawn, the water collecting in the hole is entirely fresh to 
the taste. Moreover, there is fresh water seeping out to the surface 3 or 4 meters 
down the beach, and forming a tiny rivulet from the 5-foot level downward. 
The only place about the harbor where Lil@opsis is not evidently associated with 
fresh water is at 60 north by 1,050 east, where, however, it is just beside the tide- 
stream, the water of which is only brackish, at the surface, at the time it covers 
the area in question. 

On the west shore, as on the east side, the upper boundary of the pure growth 
of Spartina glabra is less regular where the beach is shaded or saturated with 
fresh water. The plants succeeding the Spartina at its upper limit are different 
as these conditions differ. The three species with which Spartina is most often 
mingled at its upper margin, and by which it is displaced slightly higher up, 
are Spartina patens, Distichlis spicata, and Scirpus americanus. 

In regions where the beach is gently sloping, and well drained between the - 
6 and 8 foot levels, S. glabra is usually succeeded by 8. patens or Distichlis, and 
commonly these are mixed. The distribution of the areas occupied by these 
smaller grasses will be given in detail in discussing the next higher belt. We 
will simply cite examples here to indicate conditions found at the tension-zone. 
At 1,660 to 1,700 north, for example, S. glabra meets S. patens at the 6.5-foot 


SPARTINA GLABRA ASSOCIATION 45 


level, and with very little intermingling the S. patens becomes as completely 
dominant a meter or two above (%. ¢., inshore from) the meeting-line as 8S. 
glabra is a meter or two below the line. Mixed with the S. patens, a little 
higher up are scattered plants of Distichlis, and, in the wetter portions, of 
Scirpus americanus. A few dwarfed, scattered shoots of S. glabra are found 
even as far up as 7 or 7.5 feet. On the well-drained areas the tension-zone 
between the Spartina glabra and the S. patens is much narrower and the last 
scattered stalks of the S. glabra get very little above the 6.5-foot level (e. g., 
at 840 to 900 north). It seems clear that elevation of the soil is the condition 
favoring the success of S. patens in the competition. Thus, for example, at 
1,760 north there is a complete island of S. patens on soil at 7.25 to 7.5 feet, 
surrounded entirely by 8. glabra on soil running up to about the 7-foot level, 
the zone of the latter on the upshore side being 1.5 meters wide. The elevation 
of this patch of soil above its immediate surroundings on all sides, with the 
better drainage thus allowed, was the only discoverable cause of the difference 
in its vegetation. : 

On parts of the west shore where fresh water is abundant 8. glabra encoun- 
ters Scirpus americanus at its upper margin. It is in these areas that we find 
the most interesting and diverse behavior of the salt reed-grass and its com- 
petitor. Hach is dependent upon the character of the soil, its fresh-water 
content, and the amount of shade to which it is subjected. In general, these 
two species, when growing on wet shores, mingle much more freely and widely 
than do 8. glabra and S. patens. For example, at 1,220 north S. glabra 
nearly 2 meters tall becomes mixed with Scirpus americanus at the 6-foot 
level, and then continues on upward to the 7.25-foot level. The Scirpus 
occurs here on soil between the 6 and 8 foot levels that is more or less covered 
by fresh water at low tide, while the Spartina is found as usual on soil above 
the level of running fresh water. At other points nearby (1,325 north), where 
the fresh water, though evidently present in the soil at higher levels, does not 
break out as a rivulet till the 5 or 4 foot level is reached, Scirpus gets down to 
the 5-foot level on higher lumps of peat. In this area the Spartina ceases at the 
— 6.25-foot level, with plants of 6 or 7 dm. in height. At 1,700 north the 
Spartina meets the Scirpus at 6.5 feet, where the latter immediately becomes 
dominant and continues up to the 8-foot level, with only the barest sprinkling 
of dwarfed Spartina plants between 6.5 and 7 feet. In general, then, where 
fresh water is present on an unshaded shore, the Spartina glabra becomes mixed 
with Scwrpus americanus from 6 feet upward. In regions that are both wet 
and moderately shaded we have a very interesting change in the relative 
distribution of these two species. Under these conditions the Scirpus is mixed 
abundantly with the Spartina from 6 to 6.5 or 7 feet and then ceases, while 
the Spartina becomes more abundant again and continues upward in moderate 
shade to 7.5 or even to 8 feet (¢. g:, at 740 north and near 1,350 and 1,400 north). 
The relation of the two plants at these points seems to show that the Scirpus 
americanus cannot endure much shade; that Spartina glabra can endure moder- 
ate shade, as indeed it must when submerged; that Spartina pushes up the 
beach far beyond its competitor Scirpus in shaded areas where fresh water is 
present, and where, therefore, the moisture content of the air about the leaves 
is sufficient to prevent a too rapid transpiration. 


46 THE RELATION OF PLANTS TO TIDE-LEVELS 


The other angiosperms which may mingle with Spartina glabra along its 
upper margin on the west shore are, in order of abundance, Solidago semper- 
virens, Atriplex patula, and Scirpus robustus. Of these, Solidago and Atriplex 
occasionally mingle with Spartina glabra near the 6.5-foot level (e. g., 1,250 
north), but they are usually encountered by the Spartina only when it has 
pushed farther up the beach. This is true also of Scirpus. None of them 
except Scirpus robustus (at one or two spots) is an important competitor of 
Spartina, and further discussion of their distribution may be left until we 
take up that of the plants of the next higher belt. 

The mid-littoral Spartina belt on the Marsh at the head or south end of the 
harbor is more largely developed than on any other part of the shore except on 
the eastern half of the Spit. Aside from the greater variety of competitors met 
at some points along its upper margin the general character of this broad belt 
of Spartina glabra is similar to that on the Spit. 

Since a special study has been made of the successive levels of the whole 
Marsh at the head of the harbor (mid-littoral, upper littoral, and supra-littora] 
marshes), and Professor Conard has mapped in detail the vegetation of a 
selected strip, cutting across all three of these belts (see plates x1, xxI, and 
XXII), we will here only sketch the most general features of this portion of the 
mid-littoral belt. It will be noticed at once on plate x1 that the main stream 
cuts into halves the whole marshy area south of the harbor, from the 1.5-foot 
level up to the 9-foot level. The portion on the west of the stream is chiefly 
below the 6.5-foot level and therefore largely occupied by Spartina glabra. 
. That east of the stream lies chiefly above the 6.5-foot level and therefore has 
a relatively narrow belt of Spartina at the north and a bare fringe along the 
stream. The lower limit of the Spartina across the whole northern border of 
this belt, from 200 east to 1,000 east, is between the 1.5-foot and 2-foot levels, 
a little higher on the average than on the east end of the Spit and than on the 
-Mmore open portions of the east and west shores of the harbor. The stand on 
the south shore is rather thinner at the edge, but soon attains a density com- 
parable with that on the Spit, and increases also in size as it goes up to higher 
bottom (indicated in the section of soil and vegetation, figure 3). On each side 
of the large stream, a shoal, coming just above the 1.5-foot level, begins at 50 
north and stretches northward toward the harbor. The shoal on the west side 
is being steadily taken possession of by Spartina glabra, which, during the six 
years our investigations have covered, has advanced several meters. Comparison 
of the present northern limit of the Spartina in this locality with that shown on 
a map made in 1902, by Shreve, indicates that it has pushed northward 12 
meters in 10 years. The shoal at the east of the stream is not being occupied 
by the Spartina, probably because the corner of the Spartina belt at 75 north by 
650 east is held back by an artificial bathing-beach across the south end of the- 
shoal, which is cleaned off each year. The irregularities in outline of the 
Spartina belt west of the stream, especially in the deep notch at 400 east, are 
apparently connected with the entrance of a stream that is dry in summer but. 
in winter and spring carries considerable fresh water into the harbor. 

Along the Creek and the tide-stream at 1,000 east the character of the lower 
margin of the Spartina belt differs on different parts of the stream-bank. 
Having incidentally referred to the conditions along the tide-stream when dis- 
cussing the Spartina of the east shore, we will here discuss conditions only along- 


SPARTINA GLABRA ASSOCIATION 47 


the Creek. In general we find on the concave side of each bend a steep bank 
(plate xv B), formed by the caving of the firm turf of S. glabra and 9. patens 
from the edge of the Marsh, as the soft material below is cut out by the stream. 
For example, at 100 south to 200 south on the east bank large blocks of the 
Marsh soil, 3 or 4 meters long and a meter thick, are often cracked off. These 
blocks either settle down while keeping the Spartina turf in a horizontal posi- 
tion, or become tilted over by the rapid undermining of the western side, until 
the turf stands nearly vertical. In the substratum, with the root-collar 3 feet or 
more below the present Marsh surface, stumps of Acer rubrum are found in situ. 
The top of the Marsh along this bank, from 0 to 200 south, rises to the 7-foot 
level only 2 or 3 meters back from the edge. From this level it slopes down quite 
rapidly to a level of 6 feet or somewhat less at the very margin, evidently because 
of the settling of the surface, as the soft peaty mud below it is washed away or 
squeezed out toward the stream. It is only this narrow, sloping brim that is 
occupied at all completely by Spartina glabra. The stand is often quite sparse, 
apparently because the bank caves and the soil settles more rapidly than the 
Spartina can completely occupy the new areas thus brought down to the proper 
level for it. The denser stand of Spartina here often ends quite abruptly in some 
places,. so that beyond 0.5 meter from the upper or on-shore limit of dense 
Spartina not more than half a dozen isolated plants of this grass can be found for 
5 meters along the bank. On this eastern bank, from 200 south to 500 south, 
where the bank is not being undermined, it slopes much more gradually, and the 
Spartina belt is wider. (See plate x1.) 

The western bank of the Creek, except from 350 south to 450 south, is a 
convex one. In consequence, we have an abrupt bank, with the Spartina belt 
very narrow, only in the particular region just specified, where the conditions 
are like those of the east side between 0 and 200 south. From 300 south to 
200 north the west bank is a gently sloping one with a very wide belt of Spartina. 
The stand of Spartina on this west side shows a range in density and height 
like that on the Spit and on north edge of the Marsh. It is practically contin- 
uous, except where cut through by branches of the main stream and smaller 
- side streams, or where it is temporarily killed out by flood-trash. As an example 
of the latter we may cite an area about 6 by 12 meters at 430 south by 720 east 
which was covered by flood-trash during spring and summer in 1911. In 
September 1911 not a green shoot of Spartina could be seen on this area, 
though elsewhere this grass was still fresh and green. These areas, when the 
trash is floated off again, become covered first with alge, as we shall soon see, 
and only gradually are they reconquered by Spartina, through the growing 
inward of rhizomes from the Spartina plants round about.* 

The upper margin of the Spartina belt here at the head of the harbor lies 
between the 6 and 7 foot levels. The map shows that the margin is generally 
quite regular, except for the tongue pushing upward along each stream. A 
sudden ending of the dense stand occurs rather frequently at the upper margin 
of its belt along the north shore of the Marsh (700 to 1,000 east). In some 
places on this shore the bottom rises rather abruptly from the 6-foot to the 


4In the summer of 1913 a patch of S. glabra 40 square feet in area (at 200 north 
by 1,000 east) was smothered out by masses of Ulva. When the latter was washed off 
by storm tides the dead leaves and culms of the grass were se felted over by 
Lyngbyas, Oscillatorias and Microcoleus. 


48 THE RELATION OF PLANTS TO TIDE-LEVELS 


%-foot level, all in a horizontal distance of 0.5 or 1 meter. The Spartina at 
the foot and part way up this slope is quite dense. On the upper half of the 
slope it thins out, and when the top of the slope is reached at 6.75 or 7 feet it is 
replaced by its commonest successor, Spartina patens, except for a bare sprink- 
ling of small shoots of the S. glabra in areas with wetter soil. Where, however, 
there are tide-pools farther up on the Marsh, the 8. glabra extends back along 
the edges of the draining ditches and often occupies not only the sides but 
sometimes the bottom of the pool itself, though this may lie above the 7.5-foot 
level (e. g., the tide-pool at 100 south by 900 east). Other areas, with a firm 
bottom, that lie but a few inches below the surface of the surrounding Marsh, 
and have no outlet on the surface, may bear small plants of S. glabra in rather 
dense stand—100 or 200 plants per square meter. Such an area is found at 
0 north by 1,025 east (plate xr) and another very interesting one just above 
the 8-foot level at 240 south by 1,135 east, as is indicated in plate x1, area 25. 
(See C. A. Davis, 1910.) 

Along the portion of the shore from 100 south by 400 east to 250 south by 
600 east, the upper margin of the Spartina belt much resembles that of the 
Spit. The soil here is sandy, and at the 6 to 6.5 foot levels S. glabra meets and 
mingles with 8. patens and more rarely with Distichlis. 1t also comes in con- 
tact occasionally with scattered plants, but never with dense stands, of Solidago 
sempervirens, Salicornia europea, and Spergularia. Near the fresh-water rivu- 
let at 320 south by 640 east the Spartima encounters and mingles with Scirpus 
americanus, which also occurs on both sides of the main stream beyond 400 
south. The related species, S. robustus, is mingled with the Spartina between 
the 6.5 and 7 foot levels at several points where the soil is considerably saturated 
with fresh water (460 south by 820 east, 100 south by 1,180 east). 

Some details of the distribution of these competitors of Spartina and also of 
certain rarer ones are indicated in plate x1. 

Throughout this Spartina belt about the south end of the harbor, aside from 
the competitors very near the upper margin, no other seed plants are found, 
except the small patches of Lileopsis (60 north by 1,050 east and 150 north by 
1,140 east), which grow on bottom between the 5 and 6.5 foot levels. Dr. Shreve 
records the occurrence of Limosella aquatica var. tenuifolva on the edge of the 
shoal near 199 north by 600 east, but this has not been seen in recent years. 

Most of the alge found scattered among the Spartina on the other shores are 
equally abundant here, and will be referred to again in a later section. 


THE FACTORS DETERMINING THE DISTRIBUTION OF SPARTINA GLABRA. 


Having sketched in some detail the distribution of this salt reed-grass about 
the whole harbor, and described the habitats in which it grows, we may now 
attempt to discover the enviromental factors that condition the distribution 
which we actually find. What factors have favored the entrance and persistence 
of the grass in the areas now occupied, and what factors limit its extension 
upward, downward, and horizontally along the shore? We should keep in mind 
that many of these factors probably act in a similar way on other plants, and 
that for this reason Spartina is a type whose relation to external factors is in 
many respects resembled by that of many other plants about the harbor. 

Temperature and light of the range of intensities found, so far as has been 
made out, play no decisive part in limiting the distribution of S. glabra. It 


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during such tides of levels from mean low water up to 7 feet. 


PATE Vil 





A. South Shore of Spit looking West from 200 West, showing Cross-section of 
Belt of Spartina glabra, left by Mowing. The 3 Stakes with Placards are 
(left to right) at the 4-foot, 5-foot, and 6-foot Levels respectively. 





B. South Shore of Spit, near East End, showing Zonaticn between 6 and 10 feet. 
In foreground Sueda, Limonium, Spartina patens; at left Solidago and 
Ammophila. The Numbered Stakes are set at the indicated Tide Levels on 
Beach. 


Avene 
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SPARTINA GLABRA ASSOCIATION 49 


seems to grow equally well on warm tidal flats, or where flooded by the cold 
water of tidal inlets or fresh-water streams. It is possible that it is the low 
temperature of the spring-water of the rivulets along the east and west shores 
that prevents the Spartina from gradually invading the beds of these streams. 
In certain areas along the west shore it endures considerable shade, though it 
commonly grows in full sunlight. These shaded plants, however, are at high 
levels and hence they enjoy, from the neighboring trees, about the same degree 
of protection from light and transpiration that plants at lower levels do from 
submergence. 

The character of the soil is evidently a factor of much importance near the 
upper and lower limits of the Spartina’s distribution. Between the 2-foot and 
6-foot levels Spartina may grow on mud, peat, sand, or gravel, as may be seen 
along the Spit. It has been pointed out, however, that the belt of this grass 
stops most abruptly at its upper margin on a gravel beach, just east of the 
middle of the Spit. At its lower margin, in like manner, the Spartina usually 
terminates abruptly at a point where the very soft mud succeeds the rather firm 
peat. This is equally true whether the change in character of the soil occurs 
at the 1.5-foot, the 2-foot, the 3-foot, or even at a higher level, as it does in the 
northwest corner of the harbor and about certain tide-pools. 

From these facts we might conclude that this plant is gradually advancing 
over the soft bottom and binding it together with its roots and rhizomes. But 
on this assumption it is rather surprising to find such a very regular lower limit 
of distribution at the 1.5-foot level in a harbor where this grass has been growing 
for hundreds of years. It will also be difficult to explain the greater width of 
the Spartina belt at the east end of the Spit. On the whole it seems clear that 
the firm soil bearing Spartina is in some way the product of the growth of this 
grass and that it is the conditions limiting the spread of Spartina that second- 
arily determine the extent of this firmer bottom. 

All observations thus far made on this harbor indicate that the decisive 
factors preventing the Spartina from spreading further upward or downward 
_ are those connected, directly or indirectly, with the water-level about the leaves 
or in the soil about the roots. In short, the primary factors may be considered 
under two heads—tide-levels and fresh-water streams or springs. 


TIDE-LEVELS. 

Differences in the elevation of soil above mean low water may, in the first 
place, influence the distribution of Spartina directly by determining the time 
of submergence. Upon this depends the level maintained by the salt water in 
the soil about the roots of the grass and the time of exposure of the leaves to 
the evaporating influence of the air. These differences of level, and so of dura- 
tion of submergence, may affect the distribution of Spartina indirectly, since the 
longer submergence evidently keeps the competitors of Spartina off the lower 
parts-of the beach. The duration of submergence also determines the types of 
plants that grow just above the Spartina and thus the conditions in the soil 
into which the latter must push if it is to advance upwards. 

At the lower margin of the Spartina belt at the east end of the Spit the 
soil at the 1.5-foot level is submerged for about 8.5 hours each tide, or for 17 
hours daily, and exposed for only 7.5 or 8 hours daily. In certain areas remote 
from the main tidal currents, as in the northwest corner of the harbor, the 

4 


50 THE RELATION OF PLANTS TO TIDE-LEVELS 


Spartina, as we have seen, retreats to the 2.5 or 3 foot level. It is believed that 
the long submergence affects the Spartina unfavorably by preventing the air 
from reaching the submerged rhizomes and roots. In the northwest corner of 
the harbor, out of the main currents, the water moves less, and hence the soil 
about the Spartina roots is less well aerated, and so this plant can not grow 
here at levels where it flourishes at the east end of the Spit, in better aerated 
soil, beneath the swifter tidal currents. It is also to be noted that crab and 
muskrat burrows are less abundant at the lower levels, and hence do not aid in 
aerating the soil. 

The change of water-level, due to the tides, keeps the soil at the upper margin 
of the Spartina belt submerged for 2.5 to 3 hours and exposed for between 9 
and 10 hours each tide. When covered this soil is probably nearly saturated. 
During emergence the water not only runs off the surface, but also settles out 
of at least the upper layers and, by way of the fiddler-crab and muskrat burrows, 
the air penetrates to the soil about the roots and rhizomes of the Spartina. The 
upper layers of the mud are firm enough to allow the fresh water of rains at 
low tide to run off so rapidly that little of it penetrates to the roots of plants. 

The immediate effect of the semidiurnal change of water-level on the leaves 
and shoots of S. glabra is to expose it wholly to the air and the heat of the 
sun during low tide. This occurs for 17 or 18 hours per day for plants at 
the 6-foot level, for about 13 hours at the 4-foot level, and for only about 8 hours 
per day for those at the 2-foot level. The plants thus exposed show a distinctly 
xerophytic structure in their stiff and thick-cuticled leaves, which roll up 
tightly in drying winds. The evident usefulness of these xerophytic structures 
in plants growing at 6.5 feet and lower might suggest that Spartina is kept 
from invading levels above this limit because it can not endure the longer 
exposure of its shoots to desiccating winds and sun. But, on the other hand, 
we must remember that the Spartina growing at 5 or 6 feet is as large and 
vigorous as any plants of this species found, showing that there is no consider- 
able reduction in size and vigor as this plant approaches its usual upper limit. 
Moreover, at high levels, in poorly drained soil, as, e. g., on the west shore and 
on the Marsh south of the harbor, Spartina grows to a good size, although its 
leaves are always exposed to the air. But the surrounding air is in most of 
these cases rendered unusually moist by the presence of abundant water on 
the surface of the soil or by an abundance of neighboring vegetation. 

All of these facts taken together seem to indicate that a low degree of satura- 
tion of the soil with salt or brackish water is a still more effective deterrent to 
the upward spread of the Spartina than the desiccation due to emergence above 
water-level. 

INDIRECT EFFECTS. 


It is clear that the direct effect of submergence or exposure in allowing or 
preventing the competitors of Spartina to grow at certain levels may indirectly 
affect, to a very marked degree, the distribution of Spartina itself. For exam- 
ple, the distribution of such plants as Spartina patens, Distichlhs, Salicornia, — 
and Scirpus americanus, which succeed the Spartina above the 6.5-foot level, 
indicates that these plants can endure neither as long submergence nor, per- 
haps, as high salinity of the soil water as S. glabra. We have already noted that 
S. glabra can grow up to levels as high as 7.5 or 8 feet, often mingled with 
Spartina patens, Scirpus americanus, and other plants. The most important 


SPARTINA GLABRA ASSOCIATION 51 


cause of the usual absence of S. glabra from the upper littoral region is, it 
seems clear, the competition of the plants above mentioned. Wherever the 
physical conditions allow these competitors to grow they prevent S. glabra 
from occupying levels higher than 6.5 feet. It is difficult in this, as in all 
cases of direct competition, to discover exactly how these plants of higher 
levels (e. 9., S. patens) can prevent the advance of S. glabra into the 
areas occupied by them. If it is really these competitors that prevent the 
growth of S. glabra in certain areas, it must be by some effect exercised beneath 
the soil, since we can not believe that the shoots of the larger plant can be 
crowded or shaded out. It is possible that the dense impervious turf of 
S. patens cuts off the air from the deeper-growing rhizomes and roots of 
S. glabra. This would be in accord with the suggestion offered above, concern- 
ing the absence of 8. glabra from poorly aerated mud of bottom below the 1.5- 
foot level. We are now attempting to solve this question experimentally. 

Currents created by the rise and fall of the tides apparently have little effect 
on the distribution of Spartina, except that already noted of undermining the 
turf beside the two chief streams of the Marsh, and a similar, though relatively 
slight, effect along the tide-channel, cutting through the Spartina belt at the 
end of the Spit (near 800 east). 


FRESH WATER IN THE SOIL. 

In places where the fresh water runs over the soil the S. glabra is wanting. 
Often the peat is cut away down to the gravel by the flow of the rivulet. In other 
places the fresh water merely seeps out or trickles over the peaty mud. On this 
kind of area Spartina is sparse or wanting, and its competitor, Scirpus ameri- 
canus, becomes more and more abundant as the soil becomes more nearly 
saturated with fresh water. Cases of this sort, of which there are many about 
the harbor, might seem to indicate that S. glabra can not grow in a soil saturated 
or nearly saturated with fresh water. But this Spartina does grow in the pool 
below the wheel of the old mill. The soil here at the time these observations 
were made was submerged in fresh water for 6 hours each tide, and could hardly 
become very strongly saline even at high water. It therefore seems quite 
possible that the competition of the Scirpus americanus plays an important 
part in crowding Spartina out of areas wet by fresh water. 

The usual intermingling of Spartina and Scirpus americanus in wet soils 
above the 6-foot level may quite possibly indicate that some individuals or 
strains of Spartina possess much greater ability to withstand fresh water than 
others and so push farther up the beach. Likewise, it may well be that the 
lowest plants of Scirpus americanus are really the individuals most able to 
endure salt water about both stems and roots. Only after experimental study 
of the problem can it be determined whether the position of the line of contact 
of these two species is dependent upon physical conditions directly or upon 
some kind of competition in which one plant disturbs the other physiologically. 
This study must include a determination of the power of different plants of 
the two species to endure considerable, and rapid, changes in the osmotic 
pressure of the water about roots and shoots. 


* A thin sprinkling of S. glabra grows south of the Causeway about 450 south and 
800 east at the 7.5-foot level in soil water with a specific gravity of 1.000. Turfs of 
this grass planted in the pond 200 yards south of the Causeway survived but a single 
season. 


5? THE RELATION OF PLANTS TO TIDE-LEVELS 


The past history of this Spartina belt is indicated by stumps and other plant 
remains found in the peaty subsoil of the Marsh at the head of the harbor. It 
seems evident that the history of these Spartina marshes has been that outlined 
by C. A. Davis for the salt, tidal marshes near Boston, which have similar fresh- 
water deposits, stumps of trees, and other features like the marshes we are 
describing (see Davis, 1910, p. 635, ff.). The minimum amount of subsidence, 
as indicated by the plant remains found in the section of the Marsh on the east 
bank of the stream at 100 to 200 south, is about 6 feet. It is difficult to see how 
these remains can have attained their present relation to tide-levels by change in 
magnitude of the tides or by the settling of a floating bog, as held by D. W. 
Johnson (1913). We know of no evidence for the former change, and the fact 
that the salt-marsh peat does not overlie the parts of the gravelly shore (e. g., 
near 100 to 300 south by 1,200 east) above the present marsh-level, seems to 
exclude the latter explanation. 


2. THe ALG& oF THE Mip-LiTToRAL MarsuH (1.5 To 6.5 FEET). 


The number of species of alge growing among the Spartina, on the natural 
shore lying between the 1.5 and 6.5 foot levels, is quite large. At least 36 species 
have been collected, and the distribution of most of these has been studied with 
some thoroughness. The classes and genera represented here, many of them by 
small patches or scattered individuals, are the following: 

Schizomycetes: Beggiatoa. 

Schizophycee: Anabena, Chroococcus, Lyngbya (2 species), Microcoleus (2 
species), Oscillatoria (3 species), Polycystis, Rwularia, and Spirulina. 

Bacillariales: Melosira, Plewrosigma, and many less abundant species of 
other genera. 

Chlorophycee: Chetomorpha, Cladophora, Enteromorpha (3 species), Llea, 
Monostroma, Rhizoclonium (2 species), Ulva, and Vaucheria. 

Pheophyceer: Ascophyllum, Ectocarpus, Fucus (2 species), Pylaella, and 

Ralfsia. 

Rhodophycew: Bostrychia, Delesseria, Hildenbrandia, and Petrocelis (?). 

Of all these species growing on the Spartina Marsh, the most prominent, 
because of their size, are Ascophyllum and Fucus. The most universally 
present are two species of Rhizoclonium (R. ripartum and R. tortuosum). In 
some places these Rhizoclonwums develop nearly pure growths of considerable 
extent, while in other habitats one or both species may form an important 
constituent, often the major one, of tangled mats, or, near the 6.5-foot level, 
of dense felts of alge. These mats or tangles are mixtures of varying propor- 
tions of Cladophora expansa, Enteromorpha clathrata, and Vaucheria thu- 
retwi?), and often include also several or many species belonging to the genera 
Calothriz, Lyngbya, Microcoleus, and Oscilatoria. The closer felts or incrus- 
tations are more characteristic of the next higher belt and will be discussed in 
that connection. Below 6.5 feet it is only on the occasional spots bare of 
Spartina that these felts of alge invade the present belt. They occur on the 
mud at the edge of the rivulets and between the stems of Spartina, and some- 
times grow upon the stalks and stubble of this grass. 

Keeping in mind the general constitution and distribution of these com- 
posite mixtures, we will now discuss the species of alge occurring on this mid- 
littoral marsh in systematic sequence. 


ALG® OF MID-LITTORAL MARSH a 


SCHIZOMYCETES. 

Of the bacteria only one species is at all prominent in the thallophyte flora 
of the sublittoral belt. This is an undetermined species of Beggiatoa, which 
frequently forms stringy white coatings over the bottoms of the tiny rivulets of 
salt water which run off the marshes or out of the banks of the ditches and 
larger streams. It occurs between the 3-foot and 6-foot levels, always on 
bottom that is continually covered by the trickling water while the tide is low. 


SCHIZOPHYCER. 

Of this group there are 12 species on the Spartina marsh and along the 
streams crossing it. The distribution will be described for each species in 
alphabetical sequence. (For distribution of important species see plate viit.) 

Anabena torulosa: This is the most abundant and widely distributed of all 
the Schizophycese of this mid-littoral belt. Its nearly circular, gelatinous, 
glistening patches are from 1 to 10 cm. in diameter, and are found on the 
firm mud among the Spartina stalks between the 4 and 6 foot levels. The 
patches are very noticeable, as they have the appearance of huge greenish-black 
ink blots on the gray mud. These are chiefly Anabena, but sometimes have 
a small admixture of Lyngbya sp. or of Microcoleus. In other places Anabena 
forms a minor constituent of loose felts over dead leaves of Spartina, which 
consist primarily of Lyngbya, Microcoleus, and Oscillatoria. Anabena is 
apparently a summer denizen of this belt. Its striking dark-green, gelatinous 
blots were entirely absent from their usual habitat in both April and September 
of 1911. The lowest level at which Anabena has been found is 4 feet. The 
highest patches were seen among the stalks of Scirpus americanus at the 7-foot 
level. This alga seems to be most frequent near the fresh-water streams. For 
example, it is found along the edge of the large marsh south of the harbor 
and along the west shore, which, as we have seen, abounds in fresh rivulets and 
springs. It has not been found forming pure growths on the south shore of the 
Spit, where fresh water is wanting. 

Chroococcus turgidus was found only occasionally, and then it was on erect 
stubble of Spartina glabra near the 6.33-foot level. 

Isactis plana is a rather frequent constituent of the felts on the Marsh, 
being usually mingled with the Lyngbyas, Vaucherwas, etc. (300 south by 625 
east at 6 feet). 

Lyngbya estuaru, L. semiplena, and two or three unidentified species are of 
frequent occurrence in the present zone, between the 4-foot and 6.5-foot levels. 
Most, if not all, of these are also found above the limits of this belt. These 
species, when found in the present belt, usually grow on the mud about the 
bases of the Spartina, and form parts of mats or tangles, in which species of 
Rhizoclonium and its allies Chetomorpha and Cladophora are the chief con- 
stituents. This mixture is found very generally about the harbor, where 
there is sufficient light for the alge between the Spartina stalks. It is 
especially frequent along the borders of the little rivulets of brackish fresh 
water that run across this belt from the upper beach. It is also seen among the 
Spartina where the latter is more scattered, at the upper margin of this mid- 
littoral belt. These same Lyngbyas are also found mixed rather sparsely with 
Anabena near the 4 and 5-foot tide-levels. 


54 THE RELATION OF PLANTS TO TIDE-LEVELS 


Microcoleus chthonoplastes occurs in rope-like bundles more or less abun- 
dantly scattered through the mats of Rhizoclonium, Lyngbya, etc., just men- 
tioned. It also occurs in nearly pure blackish-green gelatinous patches on the 
otherwise bare mud among Spartina stems between the 4-foot and 6.5-foot 
levels. It is found also in the next higher zone, being there mixed with other 
Schizophycee. 

Microcoleus tenerrimus occurs in the tangled mats above mentioned, but is 
less abundant than the last species and has not been found in pure growths. 

Oscillatoria lumosa is frequently a sparse constituent of the matted coverings 
of the pebbles on the south shore of the Spit at 6 feet and upward (e. g., at 500 
east). ‘T'wo other species also occur here, one of them distinguished from 
O. limosa by its constantly straight tips and the other by its smaller diameter, 
which is less than half of that of O. lumosa. 

It is probable that other species of Oscillatoria and of other Schizophycee 
which occur at higher levels will be found in the present belt, but the lack of 
time made it impossible to determine accurately the distribution of any but the 
more abundant species of these minute plants. 

Rwwularia atra forms shiny black pebbly patches, on otherwise bare, firm mud, 
between the 5 and 6 foot levels. It is most abundant on the vertical or overhang- 
ing bank formed by the caving off of the Marsh on the east side of the Creek 
at 100 to 200 south by 775 east. Here, in the shade of the overhanging grasses 
of the bank, many square decimeters of surface are covered more or less con- 
tinuously by patches from half to several centimeters in diameter. These 
patches are distinguishable at once from those of the Anabena mentioned above 
by their pebbly surface, greater thickness (1 to 2 mm.), and firmer texture. 

Spirulina tenutssima is occasionally found rather sparsely mixed in the 
composite mats of green and blue-green alge, seen in some parts of this belt, 
though both these and the Spirulina are more characteristic of higher levels. 


BACILLARIALES, 

Of the diatoms occurring on the beach and Marsh between 1.5 and 6.5 feet 
only two species have been noted as abundant. These are Melosira and 
Pleurosigma. 

Melosira occurs usually sparingly in the mats and felts on pebbles or stalks 
of Spartina between the 4 and 6.5 foot levels. The filaments of Melosira found 
here are of many cells in length and are apparently in living condition. It is 
not certain whether this species propagates freely here or whether the filaments 
found arise from bits broken off from the epiphytic tufts on the Zostera. 

Pleurosigma angulatum is found scattered over the felts of other alge at 
and just above the 6-foot level. 


CHLOROPHYCEZ. 

Of this group at least a dozen species have been found in the mid-littoral 
Marsh, some being quite abundant. (See plate vir.) 

Chetomorpha aerea forma linum, which we have mentioned as present on 
the bottom, is also found frequently mixed in the mats of Rhizoclonium about 
the Spartina stalks from 6 feet downward along the whole shore of the harbor. 

Cladophora (expansa?) occurs abundantly about all four sides of the harbor 
from the 4-foot up to the 6.5 or even %-foot level. In this habitat this species 


ALG OF MID-LITTORAL MARSH 5 


is commonly sparsely branched, often simple for 15 or 20 cells. (The cells are 
30 to 45u wide by 200 to 600u long. It is often found mixed with Enteromorpha 
clathrata, Rhizoclonwum, Vaucheria, or various blue-green alge, but it may 
also develop nearly pure growths, forming loose fluffy tufts on mud about 
the steps of Spartina glabra (e. g., 2,000 north by 825 west). In the neighbor- 
hood of fresh-water rivulets this Cladophora keeps up 10 or 15 cm. above the 
level of the water during low tide. It evidently does not stand well a con- 
stant immersion in fresh water, though it must of course often be washed 
with rain-water during low tide. On April 8, 1911, no tufts of this alga were 
found along the shore. However, tangles of this same Cladophora were present 
in the Inlet on this date in great numbers. It seems certain that spores from 
these tufts must reach the shore, but find the conditions there less favorable 
than in the summer. This is probably because of the absence, in April, of the 
Spartina to give shade, to prevent desiccation, and also to hold the tangled 
threads of the alga. 

Of the two species of Hnteromorpha found in this zone HL. clathrata is the 
most generally distributed. We have already noted that dense tangles, many 
yards in extent, may float up from among the Zostera and drift ashore to settle 
on the Spartina, crushing it down by their weight. Parts of the masses of 
Enteromorpha that sink in shaded places between the clumps of the Spartina 
may persist in a living condition for days or weeks. Far more important are the 
widespread smaller mats or tangles of H. clathrata covering the mud at the 
base of the Spartina stalks, either as pure growths or mixed with several other 
green or blue-green alge. The H. clathrata of these mats adheres rather firmly 
to the mud, apparently by the silting in of its older parts. It has shorter 
branches and a smaller diameter than the tufted plants found on the Zostera. 
Streaming tufts, like those on the Zostera, are occasionally found in the 
present belt, in tide-pools (e. g., at 0 south by 1,110 east at 3 feet and 
at 0 south by 1,165 east at the 4.5-foot level). In streams where the water 
is quite fresh for a considerable time at each low tide the H. clathrata is 
absent. It is found, however, at higher levels on the banks of such streams, 
out of reach of the fresh water (460 south by 680 east). In April 1911 this 
Enteromorpha was found on the stubble of the Spartina, but not nearly as 
abundant as it usually is in July and was in September 1911. 

Enteromorpha crinita has been found between the 3 and 5 foot levels asso- 
ciated with H. clathrata and with Rhizoclonium, e. g., on the eastern banks of 
the Creek at 200 south (see p. 59). 

Enteromorpha intestinalis, the third species of this genus found in the harbor, 
is characteristic of just those habitats within this belt which are flooded with 
fresh water for from 5 to 10 hours at each low tide. In fact, this species is 
almost entirely confined to parts of the shore near fresh-water streams. Only 
a few smaller plants have been found elsewhere, as, for example, along the 
wharves, on stakes or buoys in the middle of the harbor, or in the channel to the 
Outer Harbor. The largest plants seen were those on pebbles in the tide-pools 
of the side-channel near 50 south by 590 east from 1.5-foot to the 2.5-foot 
levels. The water standing or running over these plants at low tide is but a 
decimeter or two in depth and is nearly or quite fresh. Under these conditions 
E. intestinalis reaches a diameter of 3 or 4 cm. and a length of 5 or 6 dm. In 
the Creek itself #. intestinalis is found scattered sparsely as far up as 450 south 


56 THE RELATION OF PLANTS TO TIDE-LEVELS 


at the 5-foot level, chiefly aside from the deepest parts of the channel. It is 
most abundant in rapids of this stream near 300 south at the 3-foot level, where 
it occurs along with Monostroma and living barnacles. These facts seem to 
indicate that the movement and aeration of the water are of advantage to the 
Enteromorpha or of disadvantage to its competitors, and that it can endure 
long immersion in fresh water. The densest stands of H. intestinalis found 
were those of the rapids of the Creek and those about the outlets of artesian 
wells on the east side (1,440 north and 1,535 north). We have already men- 
tioned the Hnteromorpha growing on the bottom near these well outlets. It is 
also found less abundantly on the wall of the wharf below these outlets, from 
the 1.5 to the 3-foot level. Here it is mixed with a Monostroma that crowds out 
the Hnteromorpha from the part of the wall immediately below the outlets, 
which is actually flooded and not merely splashed with fresh water. 

Another interesting type of habitat for H. intestinalis is found in the fresh- 
water rivulets that run down across the shore from the high-water mark (plate 
vil). There are many of these on the west side of the harbor and several on the 
east side. The most interesting one on the latter side is the rivulet on top of the 
wharf at 1,000 north. The fresh water comes down through a ditch from a spring 
at some distance above the shore-line, and finally escapes between the big stones 
of the wall at the 5-foot level. In this stream H. intestinalis is found not 
merely among the Spartina on the bottom at 1.5 feet, but on the stones of the 
wall where washed by fresh water and also on the pebbles in the stream on top 
of the wharf, where at the 7-foot or 7.5-foot level, this alga is associated with 
Scirpus americanus, a characteristic plant of the upper littoral belt. This alga 
grows on pebbles and stones in the bottoms of streams on the west shore, where 
it is flooded with fresh water at low tide (1,050 north, 1,400 north, etc.). It 
often occurs here from the 7-foot level downward across the whole width of the 
mid-littoral belt. 

On the banks of the little streams which are at all exposed to drying out at 
. low tide, other alge take the place of this Hnteromorpha. In the pool below 
the flume of the mill at 500 north on the east side H. intestinalis grew at the 
5-foot level where immersed in pure fresh water for 8 hours or more at each 
tide. Even at high tide the flow of fresh water was abundant enough probably 
to prevent the pool from ever becoming really salt. In this pool Ascophyllum 
was the only alga growing along with the Hnteromorpha. In the fresh-water 
rivulets of the east and west sides of the harbor we find with Hnteromorpha the 
red blotches of Htldenbrandia and several green alge which form incrustations 
on the submerged pebbles. The association of EH. intestinalis with fresh water 
is so characteristic about this harbor that one not only expects it wherever fresh 
water is found, but suspects the presence of fresh water wherever the alga occurs. 
Thus at 1,850 north, between the 2 and 5 foot levels, #. intestinalis occurs in a 
rivulet of water starting from about the 5.5-foot level. This water proved to be 
really fresh, and not merely salt water draining out of the marshy shore, as was 
at first supposed. | 

In all of those cases mentioned above where the Hnteromorpha grows at or 
above the 7-foot level, it is evident that the alga must in the average tide be 
immersed in fresh water for 10 or 11 hours at each tide. Moreover, during 
each series of neap tides these plants may not be wet by salt water for several 
days. These facts, together with the fact that certain species of Hnteromorpha 


oe bathe ¢ aes 


a3 A eps Oe Rae aa We 
PALMCEYD THA) “osuy? 
Lk, lnndonh, © a 


a te 


‘ 
\ 


wo neha ww on Says 


ee eee 


Qe Se 





JOHNSON AND YORK. 

















1200 



































PLATE VIII, 


14.00 E._ 






































































































3000 N. 


Sympon PLANT INDICATED. 
Ab Anabaena 
, Cx Calothrix 
800 
Ct Chaetomorphe 
Cl Cladophora 
Cy Clathrocystis 
2600 Ec Enteromorpha clathrata 
Ei Enteromorpha intestinalis 
I Tlea 
lg = Lyngbya aestuarii 
2400 Ll = Lyngbya lutea 
Ls Lyngbya semiplena 
Mn Melosira nummuloides 
Mb Melosi rret 
moan 3 Melosira borret 
Mi Microcoleus 
M  Monostroma 
R Rhizoclonium 
2000 Rv Rivularia atra 
Sp Spirulina 
Ux  Ulothrix flacca 
ae Ulva 
Vv Vaucheria 
tc f[ecanora 
1600 
1400 
1200 
1600 
800 
600 
400 
200N. 
Scale 1:4000 
() 100 «4200 300 400 SOOFEET WELL FW & 
(0) 
ELEVATIONS AND DEPTHS IN FEET 
a ~|Tide lines (even feet) 
2005, Tide lines (odd feet) 2005S. + 
Wort tine 
Location of range stake 400 
400 
aaa Lower limit of Spartina glabra 
sr] Limits of Zostera marina cone 
600 S, 














1200 






1400 E. 


1000 W. 800 600 400 200 W. 


Map or Inner Harpor, Corp Spring Harpor, SHOWING THE DistigsuTION OF THE MORE IMPORTANT 
ScHIzOPHYCEAE, DIATOMEA! AND CHLOROPHYCEAE. 





ALG OF MID-LITTORAL MARSH oF 


grow inland far from the sea, suggested the possibility that the present species 
might persist indefinitely in fresh water. Miss Stella G. Streeter, in the summer 
of 1910, attempted to determine this experimentally by moving pebbles bearing 
E. intestinalis to a point in the same stream above the reach of the tide. This 
resulted in the death of all plants thus subjected to a constant immersion in 
fresh water, in 16 or 18 days. Similar experiments with Monostroma, which 
is likewise associated with fresh water, showed that it is even less resistant to 
constant submergence in fresh water. The reason for the association of 
Enteromorpha intestinalis with fresh water has not been determined. It is 
conceivable that it may be because the Hnteromorpha finds these habitats 
endurable for it and at the same time free from many competitors which it 
would encounter in really salt water. The fact that H. intestinalis grows in 
tide-streams, or on open shores, suggests also that the movement of the water 
in fresh-water streams may make these favorable habits. 

Some observations were made on the rate of growth of sporelings of this 
species of Hnteromorpha and of H. clathrata. Blocks of wood and stones placed 
beside H. intestinalis in its native habitat showed a crop of young plants from 1 
to 2 mm. high in 3 weeks’ time. Logs of a floating raft placed in the water on 
July 15 had many plants of H. clathrata on them by August 15, and they were 
8 to 10 cm. long. The rate of growth in length of mature plants of H. intesti- 
nalis was also measured by Miss Streeter. In plants averaging 60 mm. in 
length at the start Miss Streeter found an average daily increase, during 20 
days of observation, of 2.5mm. The maximum daily increase observed was about 
4mm. Unfortunately these plants, even when left undisturbed in their native 
tide-pools, do not long withstand even the slight handling necessary for 
measuring them. In most of the plants the terminal portion began to die off 
in less than a week’s time. 

Ilea fulvescens is a second alga that is associated almost exclusively with 
fresh-water inlets of the Inner Harbor. This species forms smoky, olive 
green or brown flexuous threads, about 1 mm. in diameter and from 5d to 10 cm. 
long. It is found streaming from pebbles of the bottom, in the swiftest current, 
of these streams at levels between 1.5 and 7 feet above mean low water. It 
occurs most abundantly in the Creek, where in most years it covers many 
square meters of the bottom. In larger rivulets of the west shore Jlea has been 
found in one or two summers on constantly submerged pebbles between the 
6 and 7-foot levels. It has also been found at one or two points on the south 
shore of the Spit. But here, instead cf forming free streaming filaments, we 
find short threads of the I/ea, apparently in living condition, felted in with the 
other alge that coat the pebbles of the beach between the 6 and 7 foot levels. 

Why an alga so abundant each summer in the main stream should be rela- 
tively so scarce in the other streams about the harbor, it is difficult to under- 
stand. Apparently the conditions are closely similar in the two cases. On the 
other hand, it is not easy to see what common factors or conditions may 
determine the occurrence of this alga both in the fresh-water streams and on the 
beach of the Spit, since the latter is absolutely devoid of fresh water except such 
as falls in rain. Jlea is apparently an early summer form in this harbor; at 
least it was entirely wanting in the main stream, and absent from one or two 
of its other habitats on September 28, 1911. 


58 THE RELATION OF PLANTS TO TIDE-LEVELS 


Monostroma latissimum is a third green alga which is associated very con- 
stantly with fresh-water inlets about this harbor. This alga forms small sheets 
from a few millimeters to 5 or 6 cm. broad attached to pebbles of the bottom in 
most of the fresh-water streams about the shore, to rocks of the wharves below 
the fresh-water inlets, and more rarely to the stalks of Spartina glabra growing 
near fresh water. In the Creek the upper limit of Monostroma is found at 560 | 
south by 820 east, at about the 6-foot level. It occurs here in the more quiet 
nooks along the banks, just out of the swiftest currents. The upper limit of 
its range is also at 6 feet in the small, very cold stream at 500 south by 860 
east. A little farther north in the Creek it grows, across its whole width, on 
pebbles at the 4-foot level. From this point northward the Monostroma grows 
in midstream on shelly or pebbly bottom, down to the 1.5 or 1 foot level, at 140 
south. In some of the small streams of the west shore, with colder water and 
more shade, this alga is found as high as the 7.5-foot level. The densest growth 
of Monostroma found is probably that near the overflow pipe of an artesian well, 
which penetrates the wall of the wharf at 1,440 north by 1,080 east, at the 5-foot 
level (plate vi11). This wall from 2 to 4.5 feet, where wet by the dripping or 
the splashing of the water, is covered by hundreds of the delicate sheets of this 
alga mixed with smaller numbers of Hnteromorpha intestinalis. Similar though 
less dense growths of this alga are found at other points where fresh water flows 
over or through the wharf (1,025 north by 1,060 east and 2,075 north by 
1,140 east). 

A reference to the tide-chart (plate v1) will show that at the lowest limit men- 
tioned above (1 to 1.5 feet), this alga will be submerged in salt water for 9 hours 
or less, according to the magnitude of the tide, and in fresh water for 3 hours or 
more. At the extreme upper limit (7.5 feet), on the contrary, it is evident that 
this alga is exposed to fresh water for several days continuously during each 
series of neap tides. 

The chief competitors for standing room on substrata suitable for Mono- 
stroma are evidently Enteromorpha intestinalis and Ilea fulvescens. The former 
is abundant only near the lower limit of the Monostroma where the latter is 
sparse. ‘The Jlea, on the contrary, is densest at just about the same levels in 
the stream, and under the same conditions of salinity as the Monostroma. In 
this region of approximation of these two species the rocks in the swiftest cur- 
rent are occupied by Jlea, for which habitat its filamentous form and lubricous 
surface especially fit it, while Monostroma, with its broad and relatively deli- 
cate sheets, lives in less turbulent water. The two species are actually found 
together in considerable numbers, chiefly in regions of moderately swift cur- 
rent. Shade, from plants along the banks of the stream, is apparently a factor 
less endurable by Jlea than by Monostroma. 

The propagation of both species is evidently accomplished by zoospores, 
which must be capable of enduring immersion for some hours in salt water, 
while being transported about the harbor. This seems necessarily true, since 
Monostroma was practically wanting in April 1911, and yet had spread to most 
of the fresh-water rivulets in July. In September 1911 Monostroma was — 
present in about the usual numbers in streams about the harbor and a few 
plants were found on the wharf of the Research Laboratory. 

Rhizoclonium is a genus represented in the mid-littoral belt by two species, 
R. ripartum and R. tortwosum, which occur, usually together, in somewhat 


ALG OF MID-LITTORAL MARSH 59 


curly mats and tangles from the 2-foot level (e. g., 35 south by 575 east) upward, 
to and beyond the upper limit of this zone, as, e. g., along the west shore, where 
it reaches to 5, 6, or even 7 feet. These tangles include, beside the Rhizoclonium, 
smaller amounts of each of a few species of green alge and of many species of 
blue-green alge, all of which we have referred to above. The tangles are some- 
times twisted more or less tightly about the stalks of Spartina glabra and 
sometimes form rather closer mats on the mud, at the base of the Spartina 
stalks, or in tide-pools from which Spartina is absent. In still other places, 
e. g., along the steep eastern bank of the Creek at 200 south, between the 
3 and 5 foot levels, these alge occur either in an almost pure growth, or 
mingled with Hnteromorpha crinita, and are woven into almost continuous 
sheets, sometimes 2 or 3 dm. wide, a millimeter or two in thickness, and often 
a meter or two in length. These algal curtains probably start as a coating 
over the surface of the vertical or overhanging bank, which is formed by the 
caving off of the peaty mud of the high Marsh east of the stream. The filmy 
covering formed at first in contact with the mud apparently peels off below and 
hangs vertically, supported by the adherent upper edge. Growth may still con- 
tinue in these pendant sheets, which are immersed from 4.33 to 6.5 hours each 
tide, and are kept moist during low tide by the water dripping from the bank 
above. 

A very marked peculiarity of this alga is its evident inability to endure long 
immersion in fresh water, although it exists in brackish water. Along each 
fresh-water rivulet the lower edge of the mat of Rhizoclonium remains a few 
centimeters above the level of the fresh water at low tide. The same thing is 
shown by its absence from those areas of the main stream which are covered 
by fresh water at low tide, though it does occur on the edges of the tide-pool at 
35 south by 575 east at 2 feet. This pool has 6 inches of brackish water in it 
at low tide. 

In April 1911, Rhizoclontum seemed to be about as abundant and in the 
same places as in July and September 1911. This seems to show clearly that 
Rhizoclonium is a perennial alga. It is the only monosiphonous cellular form 
on shore and wharf in the summer, but in April another somewhat similar 
alga (Ulothria flacca) was abundant on wharves and on branches of the 
Ascophyllum, Fucus, and Pylaiella that are attached to the wharves. 

Ulva lactuca latissima, as we have seen, is most characteristic of areas below 
1.5 feet, that is, of the harbor bottom. It occurs, though much less abundantly, 
in the present belt also. A few plants grow on wharves or stakes, but it is 
found chiefly along streams or in tide-pools, where it is not dried out at low 
tide. Up to the 3 or 4 foot level, considerable numbers of detached plants are 
found in tide-pools. In the pool at 35 south by 575 east it occurs at the 2-foot 
level, in water that is brackish at low tide. At 2,800 north by 650 east, at the 
4-foot level, is a tide-pool with hundreds of detached plants of Ulva, which are 
but a few decimeters broad, very much curled and perforated by numerous 
roundish holes a centimeter or more across. This type, which somewhat resem- 
bles var. mesenteriformia of Collins, occurs in a few other places where the water 
becomes much heated by the sun during low tide. It is found, e. g., in small 
pools along the tide-stream through the Spartina at the east end of the Spit near 
800 east, and less-developed examples of this variety occur along the northern 
border of the Spartina zone near 0 to 150 north by 400 to 500 east. The 


60 THE RELATION OF PLANTS TO TIDE-LEVELS 


one other habitat in which Ulva occurs in this mid-littoral belt is along 
the edges of fresh-water streams and rivulets. Here the plants are attached 
to pebbles, shells, or stems of Spartina. For example, in the Creek the 
southern limit of Ulva is between 100 and 200 south. Here it occurs along the 
stream-edges at the 1-foot level, just above the surface at low tide, where the 
water is quite fresh. Northward from this point the alga becomes more and 
more abundant up to 200 north, where there is a dense growth of Ulva, especially 
on the east side of the channel. Only a few plants occur here, even in the 
channel where constantly submerged. In the small rivulets on the east and 
west sides of the harbor Ulva is found up to the 3.5 or 4 foot level, on immersed 
pebbles or on stalks of the neighboring Spartina where shaded by this grass. 
The Ulva is confined to those parts of the mid-littoral belt where the substratum, 
or perhaps the surrounding air, is unusually moist, and thus prevents the drying 
out of the plant at low tide. This view seems confirmed by the fact that in 
April 1911 numerous small plants of Ulva were found attached to the dead 
stubble of the Spartina all along the west shore, where, except near the rivulets, 
Ulva was wanting entirely in July, August, and September 1911. 

Vaucheria (thuretu?) is the last species of green alga to be mentioned as 
occurring on the shores of the mid-littoral belt. It is found either in nearly 
pure tufts or as a constituent of the compound felts referred to above, which are 
made up primarily of Rhizoclonwum, Enteromorpha clathrata, Cladophora, and 
Lyngbya estuaru. These composite felts including Vaucheria are found quite 
generally on all four sides of the harbor between the 5 and 7.5 foot levels. The 
Vaucherva is usually found in felts that are more or less protected from desicca- 
tion by shade or by unusual wetness of the soil. The pure tufts are most abun- 
dant on the south and west sides and have not been seen at all on the Spit. The 
only considerable patches seen are near fresh-water inlets, though never so near 
as to be submerged in fresh water for more than an hour or so at each tide. Good 
. examples of these turfs are the dark-green ones, a meter or more square, found 
on the banks of the Creek, at 300 south by 790 east at the 4-foot level; at 400 
south by 800 east at 5 to 6 feet, and that near 500 south by 750 east at 6 feet. 
A seeming exception to this constant association of the Vaucheria turfs with 
fresh water is found at 1,714 north on the west shore at 6 to 6.5 feet. But 
though no fresh water is running over the surface at this point, it 1s seeping 
through the soil in quantity sufficient to make the soil-water here at low tide 
decidedly less saline than the water of the Spit beach or the water of the harbor. 
In speaking of the occurrence of Lilwopsis at this point, we have already men- 
tioned the fact that small trickles of fresh water come out of the beach between 
the 4 and 5 foot levels. 

The turfs of Vaucheria are also found in wet places in the upper littoral 
levels of the Marsh south of the harbor, in wet areas near tide-pools, or where 
the water is apparently coming up from below. 

From the observations above given it seems evident that the presence of an 
unusual amount of water in the soil, even though it be fresh water, serves to 
protect the overlying Vaucheria from drying out. In the composite felt on the 
drier beaches, the other more resistant alge probably serve to protect the more 
delicate Vaucherta, and thus enable it to live higher up the beach than it could 
otherwise do. This same sort of protection is sometimes given to the Vaucheria 
at higher levels by the Spartina patens, as from 150 to 250 south and between 


j JOHNSON / 














JOHNSON AND YORK. PLATE IX, 


1200 i400 E. 


a Ae, 






1000 W. 800 600 400 


\ 
9X 
\ 
\ 










3000 N. 





23800 





2800 


2600 





2400 








2200 




























































































































































2000 
1800 
1600 
1400 
1200 
1000 
800 
600 
400 
\ 
-200N. 
Scale 1:4000 
0) 100 ©6200 =6300 4400S SOO FEET 
(0) 
ELEVATIONS AND DEPTHS IN FEET 
[—~|Tide lines (even feet) 
200 S. 
200 -—-----] Tide lines (odd feet) 
fromm] Wharf line 
400 
an Location of range stake ee 
EXPERIMENTA 
An] Lower limit of Spartina glabra EVOLUTI 
py Limits of Zostera marina ao) 





1000 W 800 600 400 200 W. re) 200€ 400 600 1000 1200 1400 E. 


Map oF INNER Harpor, Cotp Spring Harpor, SHowInG THE DisTRIBUTION oF THE MORE FREQUENT 
SPECIES OF PHAEOPHYCEAE AND RHODOPHYCEAR. 


By Duncan 8. Jonson anp Haran H. York, | 





PLANT INDICATED. 


SyMBOL 


At Agardhiella 

A Ascophyllum 

So Bostrychia 

Cr Ceramium rubrum 

Ce Ceramium strictum 

Da = Dasya 

DI Delesseria 

fa —_ Ectocarpus silic. amphb 
Ep  Ectocarpus confv. pennicil 
Fe Fucus evanescens 

Fv Fucus vesiculosus 

‘s Fucus vesic. spiralis 
Ge Gracilaria 

Gn Grinnellia 

H Hildenbrandia 

Pr Porphyra 

Py Polysiphonia 

Py Pylaiella 

Rf Ralfsia 

Se Scytosiphon 


The frequency of the symbols 
Suggests the relative frequency of 
the species in each area, except for. 
the very common Ascophyllum, 
Fucus and Bostrychia, whose abun- 
dance on the wharves is such that 
it can not be so indicated in the 
space available for symbols. The 
placing of these symbols on the 
landward side of the wharf line, in 
some cases is to avoid crowding, 
and still indicates that these species 
are present on the vertical wall of 
the wharf. 


ALG OF MID-LITTORAL MARSH 61 


400 and 600 east at the 6.5 to the 7.5-foot levels. There is possibly also some 
subterranean fresh water in the soil of this area, for it comes out in rivulets 
just south of this. 

PH EOPHYCER. 

The most prominent brown alge of the mid-littoral marsh are Ascophyllum 
and Fucus. ‘These are the same species that dominate the same levels (1.5 to 
6.5 feet) on the walls of the wharves. On this marshy belt, however, these 
algze nowhere form a pure stand over any considerable area, since there are 
no extensive stony beaches to give them a satisfactory footing. Only on the 
east side of the Inlet and on an occasional log, stone, or shell about the other 
shores of the harbor do these alge find, between these levels, a satisfactory sub- 
stratum for attachment. (For distribution see plate rx.) 

Ascophyllum nodosum is scattered about the whole circumference of the 
harbor, and throughout the entire width of the present belt. At the lower levels 
it has much the same size and coarseness as on the wharves. At the upper levels, 
especially in places exposed to high temperatures, this alga remains smaller and 
the branches are much more slender than those of the plants growing on the 
wharves. On the shore, as on the wharves, ripe receptacles are rare during the 
summer, though abundant during the spring. The distribution of Ascophyllum 
in relation to fresh water is seen best along the natural shore. By the main 
stream, from 10 north to 600 east, ete., Ascophyllum grows 2 feet long and is 
fertile, but it keeps just above the level of the fresh-water stream at low water. 
Again, at 1,000 north on the east shore, there is a vertical strip of stone wall 
3 feet wide, horizontally, that is bare of Ascophyllum, where a fresh-water 
stream runs through the wall. In the pool of fresh water just south of the mill, 
Ascophyllum is found on logs and stones about the border, but always just above 
the level of the surface of the pool at low water, which is at 5 feet. Only at two 
spots along the eastern side of the harbor (1,435 north and 2,050 north), where 
the water from artesian wells flows over or between the pebbles of the bottom, 
does Ascophyllum seem to grow where it is wetted with running or splashing 
fresh water at low tide. Closer examination of the plants near the outflow from 
these wells shows that only part of the thallus is actually submerged in the fresh 
water during any one low tide. The other branches are held above the water by 
the submerged ones and by those stones and pebbles between which the water is 
flowing, as they would not be in the more definite channels of the streams along 
the natural shore of the harbor. In the spray-zone also not all parts of the sur- 
face of a plant are completely flooded all the time. On the whole, it seems 
evident that these plants of Ascophyllum, in common with those of the wharves 
and shore, are really enabled to carry on some gaseous exchange with the air 
during low tide. It must, of course, be remembered also that in the turbid water 
of the Inner Harbor the light supply of even slightly submerged plants would 
be greatly diminished. The exclusion of light would probably be just as efficient 
a cause in keeping Ascophyllum above low-water level as would be the cutting 
off of the more ready access to CO,. We may note also that while the lower limit, 
in the Inner Harbor, of Ascophyllum and its associate Fucus is about 1 to 1.5 
feet above mean low water, they occur at 1 or 1.5 feet below mean low water on 
the rocky beaches of Long Island Sound. In this latter habitat the water is 
much clearer and so would allow more light to reach plants that are continuously 
submerged, as some of these plants of Ascophyllum and Fucus must be for 


OZ. THE RELATION OF PLANTS TO TIDE-LEVELS 


several tides in succession, during each series of neap tides. But the water of 
these open shores is also much better aerated by the constant movement, and 
thus may furnish a much better supply of the necessary oxygen and CO, to a 
submerged plant than it could obtain from the water of the Inner Harbor. It is 
also true that the paraphyses of /ucus, for example, are much better developed 
on plants in the Sound, which may perhaps aid in the absorption of CO, from 
the water. Nowhere in the neighboring parts of the Sound have Ascophyllum 
or Fucus been found at more than 2 or 3 feet below mean low water. The same 
inability of these plants to withstand constant submergence is indicated by their 
absence from tide-pools. This has been noted in the cold water of Casco Bay, 
Maine, as well as at Cold Spring Harbor. 

It seems clear that the absence of Ascophyllum or Fucus below the 1-foot 
level in the Inner Harbor may be due either to the insufficient light or the 
insufficient opportunity of gaseous interchange. Only a carefully planned study 
of the problem can show definitely just how far each of these factors is concerned 
in determining this lower limit. 

Two species of Fucus (Ff. evanescens and F. vesiculosus) are distributed 
about the harbor in this mid-littoral belt. These are found along with the 
Ascophyllum wherever a stone, a sunken log, or a shell, including the shells of 
living mussels, gives them a footing. J’. evanescens occurs rather rarely on 
large stones in open places. 

Fucus vesiculosus is far more abundant and widely distributed, and is repre- 
sented by at least three distinct varieties. The typical form of the species, the 
robust one characteristic of the vertical walls of the wharves, occurs also on 
stones of the bottom. These latter are chiefly stones that have fallen from the 
wharves, and are especially abundant along the east side of the harbor. But 
this robust Fucus is also found on larger pebbles and stones in the lower parts 
of this belt far from the wharves, for example, in the Inlet or less frequently 
_ along the west shore from 600 to 2,200 north. The distribution of I’. evanescens 
and of the typical F’. vesiculosus is in general similar to that of Ascophyllum, 
except that they may grow at somewhat higher levels. Their distribution is 
apparently determined by the same factors that affect Ascophyllum. 

The variety of FP. vesiculosus which is most widely distributed on the marshy 
shore is a more slender form (probably F. vesiculosus laterifructus Grev.). 
This variety grows in habitats between the 1.5 and 6 foot levels that are more or 
less shaded by Spartina glabra. The fronds of this Fucus are attached either to 
pebbles or shells, and never, so far as seen, to the stalks of the Spartina. 
Nowhere does this variety become as dwarfed and attenuated as it does on the 
muddy shores of certain more protected near-by harbors, such as Lloyd’s 
Harbor. In this variety of Fucus we have another excellent opportunity for 
an experimental study of the factors determining a particular type of plant 
structure. (Plate xv1B.) 

Perhaps the most interesting variety of Fucus found about the harbor is F. 
vesiculosus var. spiralis (.) Ag. (plate xv1A). This form occurs between the 
1.5 and 6 foot levels, chiefly along the west and north shores of the harbor. It 
is sparse in the fringing Marsh at 50 to 150 north by 700 to 1,000 east and is 
most abundant in the large Spartina area south of the east end of the Sandspit, 
where scores of plants occur tangled together in a single square meter. This 
variety differs from all the other forms of Fucus mentioned in habit, since it is 


ALG OF MID-LITTORAL MARSH 63 


not attached by holdfasts, but simply les in curly, twisted tangles among the 
stems of the Spartina. It also differs from these markedly in structure. The 
individual plants vary in length from 1 to 3 dm., and have a nearly constant 
width from end to end of about 8 mm. The midrib is not at all prominent, 
cryptostomata and vesicles are rare, and fruiting branches have never been seen 
on this variety here during the summer season, nor on the April and October 
visits. From the absence of any receptacles on the older plants and also of any 
sporelings or very young plants, it seems evident that this variety does not 
frequently propagate itself sexually. From the mode of growth of this alga, 
in tangles not attached by holdfasts, and from the occurrence of small broken- 
off bits floating about in the water, it is highly probable that the chief mode of 
propagation is this purely vegetative one, resembling that of the well-known 
Sargassum bacciferum. | 

The question now arises concerning the relation of this form to the typical 
F. vesiculosus. In view of the absence of receptacles on F’. spiralis, the sug- 
gestion occurs that the plants of this variety may ultimately arise only from 
odspores or fragments of typical plants of FP. vesiculosus. Portions of the 
thallus of this species of the variety growing on the wharves were tangled in 
wire netting and left for four weeks among the Spartina on the Spit. At the 
end of this time the tips of most of the plants had begun to assume the charac- 
teristic spiral twist of the variety spiralis. In the following spring some of the 
spiral plants developed from the fragments showed 4 inches of spirally twisted 
thallus. It may be noted also that plants having essentially the vegetative 
character of F. vesiculosus spiralis were found by the senioor writer at Quahog 
Bay, Sebascodegan Island, Maine, in August 1911. These plants were attached 
and bore well-developed receptacles. The occurrence of fertile plants in these 
colder waters in summer suggests that the plants at Cold Spring Harbor may 
be fertile during the winter. But it seems hard to believe that no trace of the 
fertile branches should remain on July 1 or be initiated by late September. 
Unfortunately, no thorough search was made for them in April 1911. 

Ectocarpus is the only other brown alga recorded in this belt between 1.5 
and 6.5 feet on the natural shores of the harbor. It occurs sparsely and 
locally at 0 south by 670 east between the 5 and 6 foot levels. It is matted with 
Rhizoclonium at 35 south by 575 east. This is apparently identical with the 
Ectocarpus occurring in the deep part of the channel of the Creek about 150 
feet south of the last-mentioned locality. It is possible that the plants were 
simply broken-off portions floated by the water to the spots where they were 
found. But the filaments recorded seemed to be living and growing. 


RHODOPHYCES. 

The only red alge that have been found growing above the 1.5-foot level are 
Bostrychia rwularis, Delesseria leprieuru, Hildenbrandia prototypus, Petrocelis 
(cruenta?), and Porphyra lacimata. All of these except Porphyra have been 
recorded from among the Spartina of the Mid-littoral Marsh, but only Hilden- 
brandia is at all frequent in summer. 

Bostrychia rwularis, although abundant on the rocks and piles of the wharves 
at all seasons, has been found in the Spartina marsh but once. This was in 
September 1911, when a patch of several square decimeters was found growing 
on a sunken log among the Spartina just north of the wharf of the Research 


64 THE RELATION OF PLANTS TO TIDE-LEVELS 


Laboratory. Other tufts of it were found at the same point growing as 
epiphytes on Fucus and Ascophyllum attached to the same log. Bostrychia 
rarely assumes this epiphytic habit in summer, but in fall, winter, and spring 
it is common on the rockweeds, as we shall see when discussing in detail the 
alge of the wharves. 

Delesseria leprieurw is a small, smoky green alga 2 or 3 cm. high, which has 
been found only occasionally. It was first recorded in 1908 as growing on a 
sunken log at the 4-foot level near 250 north by 1,000 east. It was recorded but 
once again (1,750 north by 1,080 east at 1-foot) until September 1911, when 
it was found abundantly on a number of logs along the west shore between 
1,200 and 1,500 north near the 3 or 4 foot levels. This alga, like Bostrychia, 
has not been found among the Spartina stalks, as it apparently was by 
Holden (see Collins, 1905). It is barely posisible that one or both of them 
may occur in this habitat during the fall or spring, but the rather hurried 
searches made for them at these seasons have failed to reveal them. Delesseria 
is perhaps the best example that we have found at Cold Spring Harbor of an 
alga that is transient in character. It occurs in considerable abundance in one 
or more places in any given season and may be wanting in any one of these places 
or even in the whole harbor in other seasons. 


B. THE MID-LITTORAL ROCKWEED ASSOCIATION, ON WHARVES BETWEEN 
1.5 AND 6.5 FEET. 

The part of the mid-littoral belt that we are now to discuss is one showing 
quite definite vertical limits and characterized by a considerable number of 
alge, which are largely restricted to the wharves. There are also certain others 
which, though they may occur sparingly below this belt, or elsewhere within it, 
never reach their fullest vigor or luxuriance except on the walls of the wharves. 
It might be expected that the more natural portions of the harbor boundary 
_would offer the best opportunity for studying the distribution of alge in the 
harbor. As a matter of fact, the walls of the wharves form the only considerable 
area of proper substratum for many of the alge characteristic of this belt. 
These areas are therefore the only ones offering adequate opportunity for the 
study of the vertical distribution of some of the most important species in this 
belt, and of the factors determining this distribution. 

About 20 species of alge have been recorded as occurring on the stones, 
piles, and logs of the docks and wharves, and on parts of wrecks. A few species 
of Calothriz and Lyngbya here mentioned are more abundant just above the 
upper limit of our belt, but are mentioned here only for the sake of brevity. 
These species, arranged in systematic order, are the following: 

Schizophycee: Calothriz (2 species), Lyngbya (2 species), Oscillatoria 
(sp. 1), and Rwularia. 

Chlorophycee: Bryopsis plumosa, Monostroma (sp.?), Rhizoclonium (2 
species), Ulothria flacca, Ulva lactuca. 

Pheophycee: Ascophyllum nodosum, Fucus platycarpus, F. vesiculosus, 
Pylavella littoralts robustus, and Ralfsia clavata. 

Rhodophycese: Bostrychia rivularis, Delesseria leprieuru, Hildenbrandia 
prototypus, and Porphyra laciniata. 

By far the most prominent alge on these wharves are Ascophyllum and the 
two species of Fucus, while Rhizoclonium and Bostrychia come next in abun- 


ROCKWEED ASSOCIATION 65 


dance and in widespread distribution, though less noticeable because of their 
size. 

The two rockweeds together cover from two-thirds to nine-tenths of the sur- 
face of the walls of these wharves, from 8 to 12 inches above the bottom up to 
6.5 feet. The bottom of the harbor, near all of these wharves, except those by 
the Inlet and that of the Research Laboratory, is about 1.5 to 2 feet above mean 
low water. ‘The lowest rockweeds are attached at about the 2.5 or 3 foot level, 
and thus hang down at low tide until their tips lie on the mud, and so they 
actually cover the walls all the way down to the bottom. Hence, as one looks at 
the walls at low tide, he sees a brown band of rockweeds starting at the bottom 
and ending above with the thinned-out Fucus, quite constantly between 6.5 and 
7 feet above mean low water (plate xvi). 

While Fucus may occur throughout the whole width of this belt, Ascophyllum 
is usually confined to levels below the 5.5 or 6 foot levels. That is, the upper 
12 or 15 inches of the rockweed belt consists of Fucus alone, or of Fucus 
interspersed with a few plants of Ascophyllum, and with the relatively incon- 
spicuous Rhizoclonium and Bostrychia. In the lower 3 or 4 feet of the zone 
Ascophyllum makes up from 50 to 90 per cent of the conspicuous brown 
covering of the walls. Thus at 1,550 north on the east side, a vertical strip of 
the bottom and wall a foot in width showed the neighboring bottom to be well 
covered with Ulva. The portion of the wall between 1.5 and 5 feet bore 150 
plants of Ascophyllum, and above the 5-foot level there were 120 plants or 
plantlets of Fucus besides Rhizoclonium and a few tufts of Bostrychia. 

On some wharves a band of Rhizoclonium 0.5 to 0.7 foot high is found above 
the rockweeds. This band, which often includes some matted Lyngbyas and 
Calothrix, is frequently interrupted and not prominent when viewed from any 
great distance. 

In general then, the rockweed band is nearly continuous on the east side of 
the harbor from 500 to 2,800 north. (See plate xviir4.) On the south it 
extends from 0 to 370 east and on the west side it is found from 0 to 550 north, 
from 1,060 to 1,220 north, and from 2,090 to 2,240 north. This rockweed band 
differs little in general character on different wharves except that its lower 
boundary is higher on wharves where the neighboring bottom is high (as between 
200 and 300 east, at the south end of the harbor). The upper border may be 
unusually high on well-shaded walls. For example, in the southwest corner of 
the harbor from 0 to 20 south by 0 to 200 east the uppermost Fucus occasionally 
grows as high as 7 feet, or even slightly above this where attached to the under- 
sides of the stones and logs of the wharves or in the cracks between them. 
The density of the stand of these rockweeds on the wharves near the Biological 
Laboratory has been somewhat lessened by the removal of several boatloads 
each year to be used for the annual clambake at the Laboratory. The Mucus and 
Ascophyllum are pulled off, leaving only the holdfast and more or less of the 
basal part of the plant adhering to the wall. The renewal of the covering on 
the wall is due in large part to the development of new fronds from these 
stumps of the old plants. Such an annual cleaning off also, of course, gives 
sporelings a better chance to get started without being shaded out. 

Miss Streeter has discovered that a regeneration, similar to that mentioned 
above, occurs when the growing tips of either Ascophyllum or Fucus are eaten 
off by snails (Paludina), as they frequently are. 

5 


66 THE RELATION OF PLANTS TO TIDE-LEVELS 


It is evident that the rockweed covering of the wall may be pretty completely 
renewed by this sort of regeneration each year, if we assume that the rate of 
growth found by Miss Streeter for July is continued for most of the year. In 
careful measurements of the elongations of plants of Fucus varying from 1 to 
20 cm. in length, made daily for a month or more, Miss Streeter found an 
average daily growth varying from 0.5 to 1 mm. in different plants. Observa- 
tions on the rate of growth of sporelings, however, as determined by the 
measurement of the same young individuals at periods 3 months apart, and by 
the time taken to cover a piece of new wall, indicates that the covering of the 
wharf near the Laboratory could not be renewed in a year’s time. 

With the above-noted general characters of the rockweed association in mind, 
we will now discuss the individual species of which it is composed, in the 
systematic order indicated on page 64. 


SCHIZOPHY CE. 

Most of the members of this group found in the rockweed association occur 
in small blackish felts or gelatinous patches, occasionally on stones, but chiefly 
on piles or dock logs. The peculiarities of each species of this class are indicated 
below. 

Calothrix fusco violacea occurs in blackish felts 1 or 2 cm. wide, several 
centimeters long and 1 to 2 mm. thick. This has been found rather generally 
about the harbor between the 6 and 8 foot levels, on stone (as at 1,050 north by 
450 west at 6.5-foot) or on wood (as at 2,200 north by 1,230 east near the 7.5- 
foot level). At these levels it is evident that the plants must withstand long 
exposure to desiccation and to rain, the last habitat mentioned above being the 
high-water line of neap tides. It is noteworthy also that this species seems to 
grow higher on wood, which has the capacity for absorbing and conducting 
water more readily, and therefore probably keeps the algee more moist when 
above the water-level than they would be on stone. Another Calothriz, which 
~ resembles C. scopulorum in the size of its cells, was found under the mill at 
500 north by 1,000 east at the 6 to 7 foot levels, on a wooden post, wet by a spray 
of fresh water at low tide and by salt water at high tide. Calothrix crustacea 
prolifera occurs between 7 and 8 feet on logs of the Research Laboratory Wharf. 

Lyngbya sp. was found on the post just referred to above. 

Lyngbya (sp. 2 to 4.54 in diameter, with tortuous tips) formed felts 1 mm. 
or more thick on the same post and on piles and pieces of wreck between 1,100 
and 1,230 north on the west shore at the 6.5 to the 7 foot level. 

Oscillatoria (at least two species) was found at the 7-foot level on the wharf 
of the Research Laboratory, on the wreck just south of it, and also on the bell 
of an hydraulic ram operated by fresh water near 2,830 north on the west shore. 

Rwularia (sp.?) formed dozens of blackish gelatinous disks 0.5 cm. in 
diameter on logs of a wreck at 1,240 north by 575 west, between the 6 and 7% foot 
levels. 

These few blue-green algee were not especially sought for on all the wharves 
about the harbor, and hence might possibly have been found elsewhere in some ~ 
seasons. Perhaps each of them may be found to be generally, though sparsely, 
distributed on similar substrata at similar levels. Several of them, in fact, 
were found on the beaches between the same levels. We are clearly safe in 
concluding that the species of these simple alg are confined, like most other 


ROCKWEED ASSOCIATION 67 


plants of the harbor, within definite and quite restricted tide-levels, though 
here, as with other forms, it will take further study to distinguish the exact 
factors determining distribution. 


CHLOROPHYCEZ. 

The only species of this group which are at all prominent on the wharves 
are Rhizoclonium tortuosum and R. riparium, except for Ulothria flacca, which 
is abundant in winter. The first two alge are more abundant and widely dis- 
tributed on the wharves than any other alge save Ascophyllum and Fucus (see 
plate viir). 

Rhizoclonium: The two species of this genus form a distinct green band 
above the upper margin of the rockweed zone, including some of the wall sur- 
face within the mid-littoral belt, and often extending some inches above this. 
The upper limit of Rhizocloniwm in more exposed places may be at 6.75 or 7 
feet, while in more protected places between stones of docks, on the north side 
of a wharf, or on projecting stones or piles, it may get up to 7.5 feet. In rare 
instances, when the places are very well protected, it may go even to 8 feet. 
The lower limit of this alga, where there are otherwise unoccupied spots on 
stones or piles, is at 3 or 3.5 feet. In those rare and small areas about the 
wharves where Fucus or Ascophyllum are nearly or entirely wanting over the 
whole vertical height of the wharf, the Rhizoclonwwm may form a distinct 
though thin green band on the wall 3 or 4 feet in vertical width. 

Any of the various kinds of rock in the walls seem to furnish a suitable 
substratum for the Rhizocloniums. The upper limit of distribution of Rhizo- 
clonium is apparently determined chiefly by the amount of desiccation which 
it can endure. ‘This is evidently dependent not only upon the level at which the 
plant grows, but also on the direction in which the wall faces and the presence 
of damp and shaded crevices between the stones of the wharf. The usual 
absence of Rhizoclonium below 6.5 or 6 feet is due to the presence there of its 
more vigorous competitors, Fucus and Ascophyllum. In those places where 
Fucus and Ascophyllum are absent and Rhizoclonium present, the lower limit 
of the green alga is perhaps determined by the long submergence of habitats 
below the 3-foot level. This may well be of considerable importance in a harbor 
where the water is usually decidedly turbid near the wharf. This water is 
relatively opaque to light, and thus would prevent, or diminish, photosynthetic 
activity in the Rhizoclontwm during some 6 or 7 hours each tide. We shall 
note facts later which indicate that these same factors are concerned in 
determining the limits of this alga on the beach and Marsh. In April 1911, 
Rhizoclonium seemed just about as abundant as in July, and with the same 
distribution. 

The other species of green alge found on the wharves, save the epiphytic 
Ulothriz flacca, occur either singly and widely scattered or in strictly local and 
usually small groups. We will take these up for brief discussion, in alphabet- 
ical sequence. 

Bryopsis plumosa: This alga has been seen but three times, and then it was 
on the east side of the Inlet at the 3-foot level. Only two or three tufts of it were 
found here, though it is scattered generally in the Outer Harbor, and scores of 
dense clumps of it are found each summer in a tide-stream entering the Outer 
Harbor 3 miles north of the Inlet. 


68 THE RELATION OF PLANTS TO TIDE-LEVELS 


Monostroma latissimum: This species is found on the wharves only at 
the relatively few points where small streams of fresh water trickle over or 
through the wall of the wharf. Just below the artesian-well outlet at 1,435 
north on the east shore, the wall is covered pretty thickly for a width of 0.5 
meter or more between the 5-foot and 2-foot tide-levels, with plants of Mono- 
stroma which are 4 or 5 cm. long. These plants are submerged in salt water 
from 5 to 8 hours each tide, and exposed to the dripping fresh water or its 
spray for the rest of each tide, about 8 to 5 hours. Another fresh-water outlet 
at 1,010 north on the east side has, in most summers, a colony of Monostroma, 
both on the rocks of the wall and on the pebbles of the stream-bed at the 7 or 
7.5 foot levels. Finally, Monostroma occurs on the brick-work about the fresh- 
water ram at 2,380 north by 990 west, from the 7-foot down to the 4-foot level. 
The factors influencing the distribution of Monostroma have been discussed in 
speaking of the mid-littoral beach or shore. 

Ulothriz: Of this genus U. (tmplexa Kutz?) has been found two or three 
times each summer in the neighborhood of fresh water, e. g., between the 6 and 
7% foot levels on piles under the mill at 500 north by 1,000 east, which are wet by 
spray from the mill-wheel. It is also found at the 7-foot level on pebbles in 
the fresh-water stream at 1,010 north on the east side. 

Ulothria flacca is a form which has not been found in the summer, but which 
was very abundant as an epiphyte and less frequent on logs and piles in April 
1911. The short, simple filaments of this alga at that time formed thin, 
grayish-green turfs over the woodwork of the wharves about the harbor. It has 
never been seen in these locations, or elsewhere in the harbor, in July or August. 
As an epiphyte on Ascophyllum or Fucus it forms a greenish coating of short 
filaments over that surface of the flat frond which is usually exposed to the 
light as the rockweed hangs down beside the wall at low tide. What is appar- 
enly the same alga also forms long, lubricous tufts on the fertile clubs of both 
-rockweeds in April. It was also frequent at this season as an epiphyte on 
Pylaella, which flourished in great numbers along the Inlet. The absence of 
this epiphytic Ulothria from the rockweeds in summer seems probably due to its 
inability to withstand the more severe desiccation during low tide at this season, 
though this has not been proven experimentally. 

Ulva lactuca: This is the only green alga of the wharves remaining for us to 
discuss. This species we have found to be abundant on the harbor bottom, and 
frequent also on the mid-littoral marsh, up to the 4-foot level, but it occurs only 
infrequently on the wharves. A few small plants have been found scattered 
about the wharf of the Research Laboratory, and still fewer on other wharves. 
Kven in April 1911, when young plants of Ulva were very numerous in the Inlet, 
they seemed to be no more frequent on the wharves. From observations thus 
far made it is impossible to decide whether the scarcity of Ulva-on the wharves 
is due chiefly to the competition of the rockweeds or is directly due to the ex- 
posure to desiccation at these levels. In view of the slow growth of the rock- 
weeds and rapid growth of the Ulva, it seems probable that the latter might, at 
least temporarily, occupy the spots bared of rockweed by the ice, were it not for 
the long exposure to desiccation it would experience on most of these walls. 


PLATE X 





A. South Shore of Spit (300 to 600 East), showing Path worn by Pedestrians, near 
7-foot level, through a Vegetation of Limonium, Suada, Salicornia, ete. 
Spartina glabra at right. QMd/nothera, Solidago, and Rhus glabra at extreme 
left. 





B. Salicornia ambigua and Limonium (in bloom) on South Shore of Spit. Among 
and over the Pebbles Algal Felts are Present. 





ROCKWEED ASSOCIATION 69 


PHAOPHYCER. 

We have already seen that two brown algew, the rockweeds Ascophyllum and 
Fucus, give character to the mid-littoral belt on the wharves. We will now, in 
somewhat more detail, take up the distribution of these and the other Phxo- 
phycee occurring on the wharves. (See also plate rx.) 

Ascophyllum: Plants of this alga of all lengths from 1 or 2 cm. up to 0.5 
meter or more are found in the harbor at all seasons. In July or August fertile 
branches or receptacles are infrequent on plants of the Inner Harbor, and 
mature ones have not been seen. In April 1911, plants with fertile clubs were 
numerous and these receptacles bore an abundance of ripe antheridia and 
oogonia. At this early spring season the receptacles were often covered by a 
turf of Ulothrix flacca. In some places Ascophyllum may form nearly pure 
patches between 3 and 5.5 or 6 feet, with 20 or more plants per square foot (plate 
xvil). In other areas it may be mingled more or less equally with Fucus, the 
two together covering the wall of the wharf. In still other places there may be 
considerable gaps in the rockweed belt oftenest filled with Bostrychia or Rhizo- 
clonvum. The rockweeds are probably ground off from these spots by boats and 
ice, and the clean surface so formed is then occupied at once by those algae whose 
spores happen to be ready for attachment and germination at just that time. 
There seems to be no difference in the capacity of Fucus and Ascophyllum to 
grow upon a given substratum within the range of the Ascophyllum. There 
seems also to be some competition between the two, arising from the shading out 
of young plants of the one by older ones of the other. Then too the plants of 
Ascophyllum, being larger, may finally overgrow and shade out even older plants 
of Fucus. It is pretty certain also that the heavier Ascophyllum often tangles 
with the F’ucus and finally tears it loose. 

The substrata upon which Ascophyllum occurs include wood, shells, sand- 
stone, some kinds of granite, and gneiss. On the wharves of the east side, 
however, it was noted that certain large yellow granite stones, between 1,000 
and 1,600 north, contrasted strongly with the dark sandstone, gneiss, and 
schist of the rest of the wall, in being entirely bare of Ascophyllum and Fucus, 
even where the immediately adjoining stones of the wall above, at the sides, and 
below, were densely covered with these rockweeds (plate 1118). ‘The general 
chemical character of the barren blocks of granite, we are told by a competent 
petrographer, is essentially like that of the well-covered blocks of gneiss and 
darker granite. Moreover, the physical character of the barren stones does not 
seem sufficiently unlike that of the covered ones to explain the barrenness of the 
former. 

Ascophyllum grows only in salt or brackish water, but it is capable also of 
enduring wetting by splashing fresh water or even by submergence of parts of 
the plant in fresh water for 2 or 3 hours of each tide. We have mentioned above 
(p. 61) its occurrence near the outlet of the artesian wells at 1,435 north on 
the east side. Perhaps different branches of each plant may be immersed in suc- 
cessive low tides. In another habitat on the east side, namely, the fresh-water 
pool just south of the mill, Ascophyllum does not grow below 5 feet, the level 
of the fresh water at low tide, but it does grow just above this where exposed to 
the air or even to a spray of fresh water for 7 or 8 hours each tide. At 1,010 
north on the east shore the rocks of the wharf washed by fresh water from the 
entering stream are bare of Ascophyllum. Asa last example, plants of this alga 


70 THE RELATION OF PLANTS TO TIDE-LEVELS 


0.5 meter long were found just at the edge of the main stream at 10 north by 
600 east where it is washed by fresh water for 2 or 3 hours each tide. 

From these examples it is evident that while Ascophyllum will. not withstand 
constant submergence in fresh water, it can endure submergence in it for 2 or 
3 hours each tide, provided that it is immersed in salt water for the rest of the 
tide. On parts of the wharf walls not exposed to fresh water the denser growth 
of Ascophyllum usually ceases at about 5.5 feet, but odspores germinate at con- 
siderably higher levels in protected places between rocks or under the shade of 
the more hardy Fucus. As these young Ascophyllum plants grow, however, 
and push out from under these protecting objects, they are subjected to severe 
desiccation during the long exposure to the air. Most of the plants that have 
started at these higher levels are killed off, and those that persist are few and 
dwarfed. The highest plants of Ascophyllum found were always in places 
protected from extreme desiccation by northern exposure or overshadowing 
rocks, piles, or Fucus. It seems clear that the upper limit of distribution of 
Ascophyllum is determined by the time of exposure to the air, though it is true 
that Ascophyllum, like Fucus, may endure drying out until it becomes brittle 
enough to crush, almost to powder, in the hand. 

The lower limit of Ascophyllum on the wharves, which is usually at 1 foot 
or more above the bottom of the wall, is probably determined by the injury, by 
burial in the soft mud, to those plants that grow nearer the bottom than this. 
Where the bottom is stony, as at 2,000 to 2,600 north, on the east side, we have 
already noted that the Ascophyllum goes to the extreme lower edge of the wall 
and then continues on over the stones of the bottom down to mean low water, 
below which it is very rarely found. (See plate xviir A.) 

Fucus: The two species found are not distinguishable by grosser characters 
that can be seen as the plants hang on the wharves. We shall therefore simply 
record the distribution of the genus without attempting to distinguish the 
-species. The plants of Fucus found vary in size from young sporelings to 
plants 2 or 3 dm. long, and with main branches 15 or 20 mm. broad (plate 
xvi11B). They occur on all the substrata bearing Ascophyllum, that is, on 
stones, shells, and piles. Fucus, like Ascophyllum, is distributed almost con- 
tinuously along nearly all the wharves about the harbor, but is not present on 
the yellow granite blocks of the wall of the east side to which we have already 
referred (plates xvir and 1118). The vertical distribution of Fucus is also 
similar to that of Ascophyllum, except that the latter is dwarfed, much less 
abundant, and often quite wanting in the upper foot of the rockweed belt, which 
belt, above 5.5 feet, is dominated by Fucus. In the more exposed places the 
Fucus is usually quite unmixed with Ascophyllum. 

Below the 5.5-foot line of the rockweed belt fucus occurs commonly as 
isolated plants or in groups of 3 or 4 plants scattered among the Ascophyllum. 
Only occasionally is a patch of Fucus as much as 0.5 meter square found at 
these lower levels. Within the zone where both Fucus and Ascophyllum grow, 
the latter apparently conquers wherever its odspores can find space to settle, 
and light enough to allow the young plants to start. The upper limit of Fucus 
moves upward on wooden wharves and on shaded stones or piles. On the wooden 
wharf at 2,230 north, on the west shore, the planks are not quite horizontal and 
the highest Fucus found is attached to the edges of these planks, at 6.75 feet, 
where water oozes out slowly after the fall of the tide below this level. It does 


ROCKWEED ASSOCIATION fO3 


not grow on the faces of these planks above 6.25 or 6.5 feet. On the east wall 
of the wharf of the Research Laboratory, also at 1,100 north, the upper limit of 
Fucus is at 6.5 feet where exposed to the sun for the whole morning, but it goes 
up to 7 or even to 7.25 feet in the shade on the north sides of piles where 
protected from the sun and desiccation. 

Fucus is prevented from occupying the very base of the walls of the wharf 
by the mud which would bury it, and perhaps also by the greater turbidity of 
the water at this lower stratum. /wucus, in general, is much less abundant in 
the lower third of the rockweed belt than in the upper two-thirds. It seems 
even less able than Ascophyllum to endure prolonged immersion in fresh water, 
as is shown by its distribution in relation to the fresh-water streams entering 
the harbor along the shore, or through the walls of the wharves. The only 
efficient competitor of Fucus on the wharf is Ascophyllum, which may shade out 
the Fucus or tear it off by the aid of a greater weight and toughness. 

Interesting facts concerning the seasonal development of Mucus were sug- 
gested by its condition in April 1911. At this time the upper border of the 
band of Fucus was marked by a series of sporelings 1 to 3 cm. high, which were 
of a reddish-brown color, unlike the usual brown of Fucus, and shriveled up as 
if killed by frost. The Fucus plants on long stretches of the wall showed at 
this season not a single well-developed receptacle, where in summer dozens could 
be found. On some parts of this wall a few plants were seen with receptacles, 
but these were immature. It is evident from what is recorded above, of the 
condition of Ascophyllum in April, that the fruiting season of the latter is 
inaugurated much earlier than that of Mucus. Observations prolonged over 
the late fall and winter are needed to determine exactly the duration of these 
fruiting seasons. 

Pyluella littoralis robustus: This alga has been found in abundance on the 
wharves, only in April 1911. Its habitat was then the wharves of the west 
shore, especially the wharf of the Research Laboratory, between 2 and 3.5 feet. 
Several times during the summer it has been found in small tufts, always on 
the Research Laboratory wharf in shaded spots between the 3 and 4 foot levels, 
usually on the north end of the wharf, and more rarely in the shadow of piles on 
the east side. This alga has nearly always been found in summer in the Creek 
near 200 south. It is evidently favored by the low temperature of the water 
here, and by the protection from desiccation at low water. 

Ralfsia clavata (Carm.) Crouan: This light or dark brown incrusting alga 
occurs on the piles and stones of wharves, especially of the west side of the 
harbor. It forms small, smooth, adherent disks each from 1 or 2 to 12 or 15 
mm. in diameter, which, when old, have a slightly wavy outline. They are at 
first thin and tightly adherent but later become thick and more easily detached. 
This form is found in summer between the 2.5 and 5 foot levels, chiefly on the 
shaded sides of piles among young plants of Fucus, along the east and north 
faces of the wharf of the Research Laboratory. In April 1911, this species was 
far more abundant at one point than it has ever been in summer. Scores of 
young colonies 2 or 10 mm. in diameter were found on stakes near the wharf 
at 400 north by 170 west at 2.5 to 4 feet. The few observations made elsewhere 
in the harbor in April showed no unusual abundance of the alga, at this season, 
in any other location. Ralfsia is not found where subjected to flooding by fresh 


72 THE RELATION OF PLANTS TO TIDE-LEVELS 


water. It grows most abundantly where partially shaded, but it is apparently 
killed out by the denser shade of large masses of Fucus and Ascophyllum or 
even by tufts of Bostrychia. 


RHODOPHYCEZ. 

The only red algee found on the wharves are Bostrychia rivularis, Delesseria 
leprieuru, Hildenbrandia prototypus, and Porphyra laciniata. Their distribu- 
tion is indicated on plate 1x. 

Bostrychia: The dense, wiry, blackish tufts of this alga reach a length of 
2 or 3 cm. and stand so close together as to cover the surface for an area of 
several hundred square centimeters. It occurs on both wood and stone on all 
the wharves, of both sides of the harbor, in spots devoid of the rockweeds, 
though often more or less overhung by them. Its vertical range extends from 
about 2.5 to 6.5 feet. In shaded cracks of wet piles or dock logs Bostrychia has 
been found abundantly as high as 7 feet, and a few plants were found at 7.3 
feet. This level is higher than that at which any other red alga occurs in Cold 
Spring Harbor or the neighboring parts of Long Island Sound. Aside from 
Hildenbrandia no other red alga occurs on the wharves or beach above the 4-foot 
level, which is the upper limit of Porphyra. 

All the fruiting plants of Bostrychia found in summer bore tetraspores. In 
April 1911 and November 1912 the plants were of the same size and had as 
actively growing initials as in midsummer. The species is evidently perennial 
and seems not to be injured by freezing, even at its extremely exposed positions 
far above the mean low water level. It is evident from the tide-curves (plate 
xxiv) that Bostrychia at the 7.3-foot level must go without being wet by salt 
water for several days in succession during each series of neap tides. It might 
chance to be splashed by an occasional wave. Aside from the fact that at this 
height it must often be washed with rain there is no suggestion from the distri- 
_ bution of Bostrychia that it can endure immersion in fresh water. It has not 
been found close to fresh-water outlets, either in walls or on the natural 
shores. 

Delesseria: This alga, though occasionally found in summer, on logs on the 
bottom, has not been seen on the wharves, except in September 1911, when it 
was unusually luxuriant. It flourished also at this time at a few points on the 
shore. It was found abundantly on piles and stones of the north end of the 
wharf of the Research Laboratory, between the 2 and 3 foot levels. The patches 
were here often several square centimeters in area and the plants 20 to 30 mm. 
high. Those that were fruiting showed only tetraspores. It is, of course, 
possible that this alga is more abundant in winter than in summer, though 
the brief examinations made in April and September did not show it to be at all 
common. 

Hildenbrandia: This ubiquitous incrusting alga forms hundreds of red 
patches, often several centimeters in diameter, on the otherwise bare stones 
of the wharves. Such patches of Hildenbrandia we have already described 
(p. 31) on pebbles in the rivulets along shore. The lower limit of Hildenbrandia 
is at about mean low water and its upper limit, on the wharves and in the 
fresh-water rivulets, is at 6 or 6.5 feet, rarely at 7 feet. The vertical distribu- 
tion of this alga is therefore as wide as that of the most widely distributed 
Schizophycere and Chlorophyceer, like Spirulina or Enteromorpha clathrata. 


UPPER LITTORAL BELT ws 


It is probably limited in distribution upward by its inability to withstand 
desiccation or constant submergence in fresh water. Its lower limit is perhaps 
conditioned by the inadequacy of light and the certainty of being silted over at 
lower levels. 

Porphyra: This alga is represented in summer by a few dozen small plants 
only. ‘They are attached to stakes or to stones or piles of the wharves at, or just 
below, the 4-foot level. It was most frequently found on the wharf of the 
Research Laboratory, though it has also been seen on the east side at 950 south 
and between 1,700 and 2,500 north. An occasional plant may be seen on a stake 
or buoy in the middle of the harbor. In April 1911 we were surprised to find 
thousands of plants of Porphyra from 1 to 2 dm. broad on the pebbles of the 
bottom of the Inlet. Examination of the wharves at this time showed that 
Porphyra was little if any more abundant there than in mid-summer. We have 
already (p. 31) suggested the possible factors limiting the distribution of this 
alga. | 

4. THE UPPER LITTORAL BELT (FROM 6.5 TO 8 FEET). 


The character of the shore in this belt differs markedly at different points 
about the harbor. On the Spit, and on parts of the east and west sides of the 
harbor, there is, at this level, a rather steep, well-drained, sandy or gravelly 
beach from 3 to 5 meters in width. At some points along the east and west 
sides and across the south end of the harbor this belt of the shore has a more 
gentle slope, a mucky soil, and is decidedly marshy. In the latter region 
especially there is a border 40 to 60 meters in width that is nearly flat. In 
spite of this marked difference in the character of the littoral region, many of 
the dominant plants found at these levels are shared in common by both the 
gravelly and marshy shores. Aside from those parts of the shore influenced by 
fresh water, the upper littoral beach and the upper littoral marsh have in com- 
mon, also, many of the less abundant plants. Because so many of these plants 
may occur on any sort of substratum, we shall discuss the vegetation of the belt 
as a whole, though occasionally speaking of “ beach” and “ marsh” to distin- 
guish a particular kind of substratum. For the sake of simplicity and clearness 
in presentation we will, however, discuss separately the seed plants and alge of 
this belt. 


A. SEED PLANTS OF THE UPPER LITTORAL BELT. (ASSOCIATIONS OF 
SPARTINA PATENS, SUA4IDA, SALICORNIA, JUNCUS, OR SCIRPUS.) 

The whole natural shore of the harbor for some distance below 6.5 feet is, 
as we have seen, completely dominated by a nearly continuous stand of a 
single grass, Spartina glabra. The only other seed plants found in that belt 
are Itleopsis and a few stragglers from the belt above. Algee of many species 
occur scattered through the Spartina, but, either because of their sparseness 
or of their small size, they are relatively inconspicuous. 
_ In the belt we are now to discuss, that lying between the 6.5 and 8 foot levels, 
no such uniformity of the plant covering is found. The character of the vegeta- 
tion here may differ greatly and sharply in immediately adjoining portions of 
the beach, where only very slight differences are apparent in the character of the 
substratum. 

The dominant plant in any one portion of the upper littoral beach or marsh 
may be any one of eight species of seed plants. In some places there may be a 


74 THE RELATION OF PLANTS TO TIDE-LEVELS 


practically pure growth of a single one of these species, as is most often true 
of the grasses or Juncus. In other places the shore may be occupied by an asso- 
ciation made up of two or three of these species. In a few regions the upper 
littoral beach is either entirely bare, in which case it may be either pebbly, sandy, 
or muddy in character, or it may bear close, blackish felts of minute alge. The 
latter are most often found on the more stable, pebbly bottoms. 

The eight species which, over larger or smaller areas, determine the character 
of the vegetation in this belt, are the following; they are mentioned in the 
order of their general prevalence: Spartina patens, Sueda maritima, Sali- 
cornia europea, Juncus Gerardi, Scirpus americanus, S. robustus, Distichlis 
spicata, and Salicornia ambigua. Only nine other species have been recorded for 
this belt. Six of these nine species that may be nearly pure over small areas, or 
may be scattered among other species just above the Spartina glabra belt, are 
these: Atriplex patula, Limonium carolinianum, Plantago decipiens, Scirpus 
nanus, and Triglochin marituma. The other three species of seed plants that 
have occasionally been seen in this belt are Atriplex arenaria, Iris versicolor, 
and Samolus floribundus. Of these, the latter two are to be regarded as inwan- 
derers, on wet shores, from the next higher belt. Their distribution is indicated 
in the list of plants and plant habitats at the end of this paper. 

Each of the eight dominant species, except Scirpus, is distributed rather 
generally about the harbor, but the Salicornias and Sueda are represented by 
relatively few and scattered plants except on the Spit, while Juncus gerardi is 
nearly absent there, though abundant on the Marsh. Scirpus americanus and 
S. robustus occur only where fresh water is present on the upper littoral beach. 
These species are therefore entirely absent from the Spit. It is only rarely 
about this harbor that Juncus gerard directly succeeds the Spartina glabra, as, 
e. g., at 200 south by 1,150 east or at 550 south by 890 east. Juncus is usually 
separated from the Spartina glabra by a band of S. patens. 

We may now discuss, in some detail, the general distribution and interrela- 
tions of the eight dominant species, and then attempt to discover the factors 
determining their distribution. Our treatment of those species occurring on the 
Marsh will be relatively brief, since this area has been closely studied and 
mapped in detail (plates x1, XxI, and XXII). 

Spartina patens: This species, as was suggested in discussing the next lower 
belt, is most abundant on the estuarial marsh at the south end of the harbor, 
though present elsewhere, on parts of the upper littoral belt which have a gentle 
slope, and no fresh water flowing over them. 'The need of these conditions 
limit the development of a continuous zone of this plant chiefly to the northern 
and western portions of the Marsh, and to the western fourth of the south shore 
of the Spit. Elsewhere this grass occurs in narrow and short strips, chiefly 
between the 6.5 and 7.5-foot levels. We may illustrate the first type of area by 
describing in a general way the growth of Spartina patens on the Marsh and on 
the west end of the Spit; then we may note briefly the distribution of the narrow 
strips about the whole shore. 

Spartina patens on the Marsh: This grass, growing in dense turfs, dominates 
nearly half the area of the estuarial marsh, east of the Creek, above the Spartina 
glabra. This area lies chiefly between the 6.5 and 8 foot levels, but at certain 
points on the Marsh this grass may get d~.,n as low as 5.5 feet (200 north by 
1,020 east), while at other points it may run up nearly to the 9-foot level (100 


SEED PLANTS OF UPPER LITTORAL BELT 19 


south by 1,000 east and 200 south by 1,100 east). The lower margin of the 
S. patens belt is usually in contact with S. glabra, while at its upper margin it is 
succeeded over all this part of the Marsh by Juncus Gerardi. At one or two 
points considerable patches of S. patens are completely surrounded by the 
Juncus (150 to 300 south by 1,150 east). The large-scale map of the Marsh 
(plate x1) shows the relations of these two species there, and suggests a possible 
explanation of these islands of S. patens surrounded by Juncus, and of other 
peculiarities of its distribution (plate x1x a). It may suffice here to say that 
the islands referred to are really lower and wetter spots. It is apparently this 
greater saturation, rather than any difference in salinity, that enables the 
S. patens to crowd out the Juncus at these points. (See plate xi and fig. 3.) 
However, it must be remembered that the evaporation of the water left in these 
low spots at high tide would give rise to some concentration which would only 
be reduced by the leaching effect of heavy rains. 

The competitors of S. patens on the Marsh which may form continuous stands 
of considerable area are, in addition to the S. glabra and Juncus just mentioned, 
Distichlis, Scirpus americanus, and S. robustus. The former is found in occa- 
sional patches not many square meters in extent, on several parts of the Marsh. 
(See plates xt and xxi.) The two species of Scirpus are more abundant at the 
upper levels of this belt, around the edges of the Marsh, where the soil water is 
nearly fresh. The region of contact of 8. patens with each of these five species 
is not usually a line, but a rather broad band, in which the competing species are 
more or less intermingled. (See especially plates x1, x1x B, and fig. 3.) 

Besides these mixtures of S. patens with other dominant species along the 
tension lines, there are several other species, scattered through the stands of 
this grass on the Marsh, the distribution of which will be indicated by Professor 
Conard. The most important of these species are: Atriplex patula, Limonium 
carolimanum, Salicornia europea, Scirpus nanus, Spergularia marina, Sueda 
maritima, and Triglochin maritima. 

Spartina patens, on the west end of the Spit: On the south shore of the Spit, 
from 590 to 1,000 west, Spartina patens forms a continuous band or belt, widen- 
_ ing from 5 feet at its eastern end to 100 feet at its extreme western end (plate 
v). The general form of the area covered by it is indicated by the relative posi- 
tion of the 6-foot and 8-foot tide-lines on plate 1. The lower limit of its distri- 
bution here is at 6.5 feet or slightly lower, the upper at 7.5 to 8.5 feet. The 
plants reach a height of 4 to 6 dm. to the top of the panicle, and form a close 
turf, with often 300 to 400 leaf-bearing shoots per square decimeter. The 
rhizomes and roots penetrate to a depth of 4 or 5 inches below the surface, and 
by their interweaving give rise to a very firm sod. All other plants are wanting, 
except an occasional plant of Limonium or Sueda or felts of algee. The latter, 
of course, are confined to the surface of the soil between the Spartina stalks. 
S. patens in this region blooms freely, except near its upper and lower limits, 
beginning early in July and continuing till early September. 

At its lower limit this grass sometimes stops abruptly against the S. glabra, 
and sometimes intermingles with the latter in a strip 1 or 2 feet in width (fig. 
2). At other points along this shore Sweda or Salicornia europea may be so 
abundant near the 6.5-foot level as to dominate an intermediate strip a foot or 
two in width between the 8. glabra and the S. patens. But even in this inter- 
mediate strip numerous plants of 8S. patens and occasional ones of S. glabra are 





_ SIOE 


716 THE RELATION OF PLANTS TO TIDE-LEVELS 


present. It is only on the eastern half of the Spit that we find a nearly pure 
band of Sueda or Salicornia succeeding the S. glabra (plates v and xiv). 

In the middle of the band of S. patens there are occasional more thinly 
covered areas where, in addition to the few dozens of Limonium or algal felts 
already mentioned, there may be scattered tufts, or now and then (as at 7.5 feet, 
950 west) a patch several feet in diameter of Distichlis. Aside from these 
plants intruders are rare, the only others being isolated tufts of Spartina 
glabra or a few scattered plants of Sueda or Sahcornia europea. 





2880N! 
8ft.level 





Tft.level 


Fig. 2.—Zonation of South Beach of Sand Spit, Cold Spring Harbor, 590 to 600 East 
by 2,850 to 2,905 North, August, 1909. By H. S. Conarp. 


Solid lines mark tide-levels; wavy lines mark boundaries of belts; dotted lines sub- 
divide the belts. 

I. Spartina glabra, 5 feet tall, in bloom at northern (shoreward) margin. Soil wet 
and muddy. 

Boundary of Iand II: A strip about 1 foot wide, with occasional plants of Salicornia 
europea and Sueda maritima of tall stature, and Spartina glabra of normal 
size. Soil a wet sandy gravel. 

Ila. Sueda maritima dominant, with Salicornia europea frequent and Spartina 
glabra occasional. There are patches of bare sandy gravel. 

IIs. Almost pure dense growth of Salicornia europwa and S. ambigua. Occasional 
plants of Sueda maritima, Limonium carolinianum, Spartina glabra, and 
Spartina patens. 

III. Densely gregarious patches of Spartina patens and Distichlis spicata. Occa- 
sional plants of Salicornia ambigua and Limonium carolinianum. Soil a 
gravelly sand with humus. 

Boundary of III and IV. Spartina patens ends abruptly. Distichlis spicata invades 
gravel by straight rhizomes. A strip about 1 foot wide of Atriplex arenaria 
and short and unhealthy Sucda maritima. Soil is gravel. 

TV. Nearly bare sandy gravel. Very sparse scattering of Atriplex arenaria and 
Sueda maritima. 

V. All fine sand with a few pebbles. A. Sueda maritima and Atriplex arenaria fre- 
quent; 3 plants of Salicornia europea. B. Mostly bare sand; 1 Salsola kali, 
1 Sueda maritima, 2 or 3 Atriplex arenaria. 

VI. Sand. A few plants of Cakile edentula and Solidago sempervirens. 

VII. Sand. Solidago sempervirens, Cakile edentula, Asparagus officinalis. Ammo- 
phila arenaria dominant. 

Belts I and IV are continuous for a long distance. Between them the components 
of belts II and III may be distributed in almost any order. 


The upper third of the belt of S. patens is rather more thinly covered with 
the grass. It has few felts of alga or plants of Limoniwm, and no Distichlis 





2300 N 
Oft.fevel 


or Salicornia. It does contain a few plants of Sueda, of Atriplex arenaria, — 


and A. patula. Only at the extreme upper edge do we begin to encounter 
wanderers from the upper levels of the beach. The commonest of these are 
Ammophila, Panicum sp., Solidago sempervirens, and Cakile edentula. Their 
frequency in the Spartina patens belt is indicated on Professor Conard’s map 
of the cross-section of the Spit (plate xiv). 


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Area, 


ip 


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10. 


11. 


12. 
13. 


14. 


15. 


. Gerardia maritima 


EXPLANATION OF PLATE XI. 


COMPOSITION OF VEGETATION IN THE NUMBERED AREAS ON THE MAP OF THE 
AWSTUARIAL MARSH, 


Vegetation. 


Atriplex patula hastata. 

Iva oraria. 

Scirpus americanus. 

Solidago sempervirens. 

Spartina glabra alternifolia. 
Plantago maritima (equally 
scattered). 
Triglochin maritima (dominant). 


. Gerardia maritima (dominant). 


Limonium carolinianum (3 plants). 
Spartina glabra alternifolia (2 doz.). 


. Aster subulatus (dominant). 


Atriplex arenaria 
Pluchea camphorata 
Spartina glabra 
alternifolia 
Limonium carolinianum. 
Solidago sempervirens. 
Spergularia marina. 


(equally inter- 
spersed). 


. Aster subulatus (dominant). 


Agrostis alba 

Spergularia marina \ (common). 
Atriplex patula hastata 
Plantago decipiens } (few). 
Solidago sempervirens 


. Agrostis alba (dominant). 


Aster subulatus (abundant). 
Atriplex patula hastata (common). 
Cyperus filiculmis (scattered). 
Solidago sempervirens (common). 
Spergularia marina (scattered). 


. Aster subulatus (dominant). 


Plantago decipiens 
Solidago sempervirens 
Spartina glabra 
alternifolia hye 21) 

Spartina patens 6. : 
Aster subulatus (abundant). 
Atriplex patula hastata 
Salicornia europea 
Scirpus robustus 
Solidago sempervirens 
Scirpus americanus. 
Spartina glabra alternifiora. 
Spartina patens. 
Agrostis alba ? (see fig. 21). 
Aster nove belgii (few). 
Atriplex patula hastata. 
Solidago sempervirens (abundant). 
Spartina glabra alternifolia. 
Spartina patens (dominant). 
Aster subulatus (few) (see fig. 21). 
Atriplex patula hastata (common). 
Solidago sempervirens (few). 
Spartina glabra alternifolia 

(common). 
Spartina patens (dominant). 
Atriplex patula hastata 
Limonium carvintanum | (common). 
Salicornia europea 
Scirpus nanus (abundant). 
Spartina patens (common). 
Spergularia marina (dominant). 


} (common). 


(common). 


Area. 
10. 


We 
18. 


19. 


20. 


21. 


23. 


25. 


Vegetation. 


Aster subulatus (common). 

Aster tenuifolius. 

Atriplex patula hastata (common). 

Limonium carolinianum. 

Spartina patens (common). 

Spergularia marina (dominant). 

Scirpus nanus. 

Spergularia marina. 

Agrostis alba (dominant). 

Juncus Gerardi (common). 

Solidago sempervirens. 

Agropyron repens. 

Ambrosia artemisiifolia (common). 

Cuscuta sp. 

Distichlis spicata. 

Plantago major. 

Polygonum sp. 

Solidago sempervirens (dominant). 

Aster subulatus (abundant). 

Cyperus filiculmis. 

Scirpus robustus (abundant). 

Spartina glabra alternifolia 
(abundant near stream). 

Spartina patens. 


Scirpus. ericar 
‘p america Paonen 


i 1 
Spartina glabra dominant). 


alternifolia 


. Althusa cynapium. 


Ambrosia artemisiifolia. 
Aster subulatus. 
Atriplex patula hastata. 
Distichlis spicata (codominant). 
Plantago major. 
Scirpus americanus (codominant). 
Solidago sempervirens. 
Spartina glabra alternifolia. 
Spartina patens. 
General mixture of— 
Agropyron repens. 
Aster nove belgii. 
Carex silicea. 
Erechtites hieracifolia. 
Holcus lanatus. 
Juncus Gerardi. 
Lycopus virginicus. 
Polygonum hastatum. 
Ptilimnium capillaceum. 
Scirpus americanus. 
Scirpus robustus. 
Solidago sempervirens. 
A recently denuded spot: 
Aster subulatus (dense stand). 
Spartina glabra alternifolia 
(400 stalks). 


. A denuded area: Aster subulatus. 
. Gerardia maritima (abundant). 
. Pluchea camphorata (dense stand). 


JOHNSON AND YORK. PLATE XI, 


OF I200E 


200% 200 N 





(Gays = 
“ = 
PUA 2 
ge awTITLii 


tt Ef 





gvo4 


2008 


JOHNSON AND YORK. 
















PLATE XI, 

an HOE G00 E 800 
2001" . 1200 E 200 N 

ay 

ec 

22 
SS ne OS 
Ne 
O-N.&S. KOS =< = 0 
. ‘i 








o 
u 
te 









LLP 
5 ae 
fo ff / 


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Vis 


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SYMBOLS Ney f ‘ a iy Us 
(BESIDES THOSE GIVEN IN TABLE F) Pear note) WAS COL fy Aulus oN i 
HH = Agropyron repens — TS, Oi Sige VIN ENN 
[|||] = Aspidzum thelypteris Ly on 
® = Aster swbulatus IS 
a = Atriplex patula hastata gris 
— =Distichlis spicata vibe 
r3e% = Eleocharis olivacea i 


SY = Juncus Gerardi 

“fo, = SCirpus americanus 

288 = Scirpus robustus 

YY = Spartina glabra alterniflora 





Yi; = Spartina patens _ 9 | 
® = Solidago sempervirens. tpi 
Tp =Tide pool 50> 
Au =Aster subulatus 
400E 600 E 


lOOOE I200E 


DISTRIBUTION OF THE CoRMOPHYTIC VEGETATION or AESTUARTAL MArsn, Cop Sprina Harpor, in 19138. By Hartan H. York 
; . sAl “ EC 


Scale 
fe) 50 100 150 200 250 Feet 








SEED PLANTS OF UPPER LITTORAL BELT 717 


The soil on which S. patens grows at the west end of the Spit is, at its lower 
margin, a compact, peat-like, saturated mud, having a depth of from 14 to 24 
inches. At the upper margin the soil bearing the sparser stand of S. patens 
becomes drier, more sandy, and much thinner, often only 6 or 8 inches deep 
between the 7.5 and 8 foot levels. 

Spartina patens on the steeper shores of the harbor: The short, narrow strips 
of S. patens found about the harbor are few and scattered on the east and west 
sides, but more numerous on the eastern half of the Spit. On the east side, 
for example, there are small patches of the grass on the wharf at 950 north, and 
still smaller ones, in which some 8S. glabra is found, on the elevated areas 
between the fresh-water streamlets on the east side of the Marsh, between 0 and 
200 north (see plates x1 and x111). More considerable areas of nearly pure 
S. patens are found on the projecting points of the shore at 200 north and 300 
north. On the west shore there are short strips of this grass at 790 to 930 north 
and at 1,010 to 1,040 north; a broad strip at 1,650 to 1,725 north; a short, 
narrow strip on elevated soil completely surrounded by S. glabra, at 1,750 to 
1,765 north. Beyond this are found but two very small patches at 1,825 north 
and 2,000 north (plate x111). The only stands of the grass on these two shores 
are at the points mentioned. 

On the south shore of the Spit, as we have intimated above, the continuous 
band of Spartina patens found in the northwest corner of the harbor does not 
reach eastward beyond 590 west. East of this we find S. patens in isolated strips 
from 10 to 100 feet long. These strips of nearly pure S. patens may occupy the 
whole width of the upper littoral beach between the S. glabra and the 7.5-foot 
level, e. g., at 280 to 390 east, 530 to 560 east, 675 to 730 east, and at 830 east. 
At other points, however (plate virB), the 8S. Patens may form rather narrow 
and short patches of pure S. patens, very nearly surrounded by the Sueda or 
Salicornia europea, which at these places form the dominant plants in the cover- 
ing of the upper httoral beach, e. g., at 250 west and at 430 to 450 west. At still 
other points the Spartina may occur scattered rather evenly through the dom1- 
nant Sueda or Salicorma europea, e. g., at 370 to 480 west and at 390 to 530 
— east. (See plate v.) 

The conditions affecting the distribution of S. patens are suggested by what 
we have said above of that distribution. It is evident that this grass can grow 
on either peat or mud, or even on sandy soil, between the 6 and 8 foot levels, if 
the soil is not flooded by salt water longer than 5 or 6 hours per day, and is not 
saturated by fresh water. How far each of these various factors works directly 
and how far indirectly has not been determined definitely in the only way it can 
be, namely, by experiment. It seems probable, however, from a study of the 
occurrence of this plant and its competitors, that it does not dominate on soils 
saturated by fresh water because it does not endure fresh water as well as its 
competitors, and therefore is driven out by them. That it will endure some 
fresh water in and above the soil seems evident from the fact that S. patens is 
found beside the fresh-water streamlets on the east side of the Marsh. 

The lower limit of S. patens is probably determined chiefly by the competi- 
tion of S. glabra, since in a few places where the latter is absent the S. patens 
goes down to the 6-foot level, and at 200 north on the east shore to the 5.5-foot 
level. Practically everywhere about the harbor S. glabra occupies the next 
lower belt, and it is evidently the unfavorable physical conditions for this latter 


718 THE RELATION OF PLANTS TO TIDE-LEVELS 


erass that keep it down to 6.5 feet and so determine the lower limit to which 
Spartina patens usually reaches. The upper limit of S. patens is probably 
determined by the physical character and salt-water content of the soil, both 
directly and by the competitors favored or excluded by these conditions. 

The lateral boundaries of the patches of Spartvna on the shore seem to be 
determined by the local characters of the soil. Thus, for example, gravelly 
sections of this upper littoral beach are pretty sure to be destitute of this grass, 
which is there replaced by Salicornia, Sueda, or Atriplex. Of course, it is 
possible that the coarser soil may be such in consequence of the lack of the 
Spartina as a binder. Wherever a fresh-water rivulet trickles across the upper 
littoral beach the band of 8. patens is broken and Scirpus americanus pushes in 
to occupy the soil saturated with fresh water. Even Spartina glabra may, in 
these moist places, push above its usual upper limit, on knobs of peat that are 
high enough to avoid being constantly wet with the fresh water at low tide. 

Juncus Gerardi: In the upper littoral belt this rush is found in dense turfs 
over very considerable areas of the Marsh (plate xx a), chiefly between the 
?-foot and 8-foot levels, though sometimes higher, as will be seen from the work 
of Professor Conard (plates x1, xx1, and xx11). Elsewhere about the harbor 
only two patches of it are found, and these are small in area and the shoots of 
Juncus are intermingled with those of other species, oftenest with those of 
Spartina patens. In one of these areas (200 north by 1,060 east at 7.5 to 8.25 
feet), the patch of Juncus is 0.5 meter wide and 4 meters long. There is here a 
sparse admixture of Solidago sempervirens and Scirpus americanus. On the 
west shore (1,700 north at the 8-foot level) there is a dense turf of this Juncus, 
of 2 square meters area, the only one on the whole west side. On the Spit this 
rush has not been seen at all. 

The distribution of this Juncus can evidently be studied best on the Marsh 
and will therefore be left for Professor Conard to discuss. We may simply 
remark at this point that the deep, peaty soil inhabited by this species is practi- 
- cally wanting, except on the Marsh. (See plates x1, xx1, and xxu1, and fig. 3, 
p. 111.) It is also interesting to note that at the one point on the west side 
where this rush occurs it is accompanied by the two plants usually associated 
with it on the Marsh, Distichlis and Spartina patens. The soil on which these 
three species here find congenial conditions is a deep, peaty muck like that of the 
Marsh, which is formed chiefiy by the sedimentary deposits from the very con- 
siderable stream that enters this side of the harbor at 1,650 north. 

Sueda maritvma in the upper littoral belt: This low, glaucous annual is 
distributed abundantly along the south shore of the Spit (plates Iv 4, v, viz B, 
and xiv), and occurs in rather frequent smaller patches on well-drained portions 
of the Marsh, but is rarely found on the east or west sides. On the Spit Sueda 
is distributed pretty generally from end to end, chiefly between the 6.5 and 7.5 
foot levels, though it occasionally gets down to the 6.25 or up to 8 foot levels. 
In some stretches of the upper littoral beach it is the dominant species in the 
belt immediately above the Spartina glabra. On other parts of this beach Sueda 
may be crowded downward into the S. glabra or upward toward the 8-foot level, — 
or occasionally be crowded out altogether, by such competitors as Spartina 
patens, Salicornia europea, or Distichlis spicata, which are the other species that 
may become dominant in this belt. In still other portions of this belt Sueda 
may occur as a mere sprinkling over areas dominated by one of the three species 


SEED PLANTS OF UPPER LITTORAL BELT 19 


just mentioned, e. g., on the Spit from 480 to 590 west. Of course, the distribu- 
tion of an annual species like this may differ somewhat from year to year, but 
not very widely, since seedlings each year can find suitable space only in the 
areas occupied in the preceding year by their parents or by their, likewise 
annual, competitor, Salicornia europea. The only chance Sueda has of invading 
the more considerable area occupied by its perennial competitors, Spartina 
patens, Distichlis, and Salicornia ambigua, is when these are smothered out by 
flood-trash, or uprooted by fishermen digging on the beach. Such free soil is 
usually promptly appropriated by either Sueda or the annual species of Sal- 
cornia. In those areas on the Spit where Sueda is the dominant species (e. g., 
780 to 820 east, 20 east to 380 west and 480 to 590 west), the band of this plant 
may be from 8 to 12 feet wide. In these stretches the Sueda may be 2 or 3 dm. 
high and stand as thickly as 100 to 200 plants per square meter. In such areas 
there may be only 2 or 3 plants per meter of Atriplex arenaria or Limonium, 
or 5 to 10 plants of Saltcorna europea, to dispute its dominance. From 20 
east to 200 east at 6.5 to 7 feet it nearly equals in quantity the barely dominant 
Salicornia europea, while between 7 and 8 feet it becomes much sparser than 
the latter (plates x111 and xiv). In other areas, e. g., from 20 to 270 east, we 
find a dozen or two plants of Sueda per square meter, scattered through the 
dominant Salicornia europea or S. ambigua. Even in this strip there are short 
stretches where the Sueda is entirely crowded out by these competitors, except 
at the very upper and lower edges of the upper littoral belt. ‘Toward the west 
end of the Spit (800 to 1,000 west), Sueda, often to the number of 8 or 10 
plants per square meter, is scattered, along with occasional plants of Salicorma 
europea, LIimonium, and Atriplex patula, through the dominant Spartina 
Patens. 

Sueda on the Marsh: On the Marsh south of the harbor Sueda is found most 
abundantly on the better-drained parts, such as the edges of ditches or along the 
tide-streams (e. g., 20 north to 30 south by 950 east and 100 south by 1,090 
east). Nowhere on the Marsh, however, does Sueda attain the maximum size 

or density of stand found on the Spit. 
~ On the west shore Sueda has not been seen at all, and on the east side it has 
been found only on the stone pier at 950 north, where it is usually scarce. 

From the examples cited above, which illustrate the more typical areas that 
have been occupied by Sueda during the time our work has been in progress, it 
will be seen that it may grow under the following conditions: It is found on well- 
drained, peaty soil (e. g., on the Marsh), or on relatively thin layers of fine- 
grained mud overlying sand or gravel (e. g., at the upper edge of the Spartina 
glabra on the Spit). Its densest stands, however, are found on the higher levels 
of the upper littoral beach, where the soil is a pretty clear sand or fine gravel. 
Those parts of this beach on the Spit where Sueda occurs over its whole width 
have a sandy or gravelly soil down to the very edge of the Spartina glabra. 
Sueda always grows in well-lighted areas, with no more shade than that fur- 
nished by the small, scattered plants of the Spartina glabra at the upper edge 
of its belt. 

Sueda is not found at any station about the harbor where fresh water is 
present in the soil, or covers the soil, or surrounds the shoot of the plant at any 
stage of the tide. There is no experimental evidence to show what amount 
of exposure to salt water and to air Sueda will endure. The fact that it occurs 

6 


80 THE RELATION OF PLANTS TO TIDE-LEVELS 


at the 6.5-foot and in a few cases at the 6-foot level shows that it can withstand 
a submergence of 3 to 3.5 hours per tide, or 6 or 7 hours per day. Its occurrence 
at the 7.5 foot and, more rarely even at the 8.25-foot level, where the shoot may 
not be submerged for several days together, shows likewise that frequent sub- 
mergence of the shoot is not necessary, even in regions with a rather dry atmos- 
phere, like the Spit. The plants of Sueda are, however, rarely so high on the 
beach that their roots can not reach to a soil that at least part of the time is 
saturated with salt water. It is to be recalled here that, as one can see on any 
calm day on the beach, the tide-water is carried up several inches above high-tide 
level by capillarity. This means that the water goes considerably higher in the 
soil than the 7 or 7.5-foot level at high water of a neap tide. That this level of 
the soil-water is a factor of some importance to the Suceda is indicated by the 
fact that, e. g., at 800 to 900 east on the Spit, this species stops near the 8-foot 
line, leaving a beach above this that is quite bare of vegetation. In this place 
there are no discoverable differences in the soil above and below the 8-foot level, 
and there are no plant competitors above this contour. It seems probable, there- 
fore, that the lack of sufficient soil-water may be the condition excluding Sueda 
from the upper levels of this shore. Unfortunately no actual determinations of 
the water-level or of the salt-content of the soil-water have as yet been made at 
this point. 

On some parts of the upper littoral beach, as has been noted above, the Sueda 
is displaced from levels between 6.5 and 7.5 feet by Distichlis or Salicornia 
europea. Whether the competition between these plants is such that some 
slight local difference in the character of the soil may give one or the other of 
these two species the advantage over the Sueda is uncertain. It is possible that 
the greater amount of humus usually present in the soils occupied by these 
two competitors may allow them to become established in these areas, while in 
the more purely sandy soil Sueda is the successful competitor. 

Salicornia europea in the upper littoral belt: This plant is found abun- 
dantly on the Spit, often in dense stands for from 5 to 20 meters along the shore. 
It is widely but sparsely scattered over certain parts of the Marsh also, while 
it is wanting from the other two sides of the harbor, except for two points on the 
eastern shore. (See plates v, XA, XIII, and XIV.) 

On the south shore of the Spit this species of Salicorma reaches its maximum 
development in size and abundance as well as in purity and density of stand. 
At the western end of the Spit (980 to 1,000 west), this Salicornia was found 
scattered thickly through a belt of dwarfish Spartina glabra some 4 or 5 meters 
wide, near the upper border of the latter. Near the 7-foot level Salicornia is 
mingled with Spartina patens, also with some Distichlis and Sueda, while at 
the 7.5-foot level Salicornia becomes completely dominant. Farther eastward 
the sprinkling of Salicornia becomes more copious, e. g., though this upper 
littoral belt from 480 to 590 west was dominated by Sueda, there was an admix- 
ture of nearly as many plants of the Salicornia. Between 380 and 480 west 
this belt is dominated by Salicornia europea, except for an occasional narrow 
bar of Spartina patens cutting across it. Between 200 and 380 west this — 
Salicornia is usually very sparsely represented, but from 200 west to 20 east it 
is, in most years, exceeded in numbers only by Sweda. Eastward from the latter 
point Salicornia dominates this upper littoral beach as far as 280 east, though 
often mixed with abundant Sueda. Next follows a stretch dominated by 


—_— 


JOHNSON AND YORK. 


j;o0d0 W.  - 800 


2600 








JO 
HNSON AND YORK. PLATE Xlt, 


ee 800 600 400 200 w. 0 200 E. 400 600 800 1000 1200 1400 E. 


3000 H Pia 
3000 N. 












2800 












































2000 














1800 


























1600 











1400 











1200 




























































































b 

neseqno\ \ SS 

LABORATORY wy 
1000 1000 
800 T 800 
600 if | 600 

N 
400 silt 400 
Beye 200N. 
ero. 4 oat 
Scale 1.4000 else \ Fe 
4 0 100-200-300 400 SOO FEET _| well ew WS a ean ‘ 0 
ELEVATIONS AND DEPTHS IN FEET 
[Lise lines (even feet) 

200 Tide lines (odd feet) 700 








ere 
| x |Location of range stake Se i 
400 | | STATION FOR \ 


400 








EXPERIMENTAL 


Lower limit of Spartina glabra EVOLUTION 
Penn Limits of Zostera marina 





600 S. 








600 S, 

















x —l 4 
1000 W. 800 600 400 200 W. 0 200E 400 600 800 1000 1200 1400 E. 


Map or InnER Harpor, CoLtp Spring Harsor, Lone Istanp, New Yorx. 


By Duncan 8S. Jonnson AND HArian H. Yor, 


This map shows the distribution of the vascular plants, found between tide marks, that are associated with fresh water, 
i. e. that grow in soil of which the soil water is made practically tresh by the proximity of rivulets or seeping fresh water. 
The plants in question are: Aspidium, Hibiscus, Impatiens, Iris, Lilaeopsis, Sambucus, Scirpus americanus and S. robustus. 
The symbols (printed in green) tised to indicate the position of specimens, or groups, of these plants are those given 


in table F. 





f 
. 


A 
¥ j ; } } 
Pe WE 
; ie Z 4) i y > 
- 7] vail 4 ay : 
21) TOG @ d_ariep ee Te ae, 


we at 


ai 





Ban tia | : I : y = er 
nes ld ; Citgo ARY . i ca! 


7% a eb  « SOF Hie = 
, “ubia ss “ i 
eonewed 9 ; wh Ehiee bo hs -) 


: ' Low 
Woe * ay 
; 
” , iy 
; ao? Way F 4 ’ wv 
a 
a : 
i Pl! 2 Poles. coe ~iele 4, I’ @ 
A = 
at "fe 
9 
" 
’ 
( ¢ 
y 
: BD J 
~~ mr 
Lo « 
>» deel ay 
~ oie 
OFTHE 
wS % yey my ? Tt? 
VATTVERSITY DF ot 
. 
ba) 
? " V4 
. 
| 
‘ 
iv } 
ii 
i 
) 
ei “ty a meitle 
= f 
, ' 
a 
- 7 6,97 4 
e . 
6 i 
\! Pee g) * “4 . 
y 
i ' = some ¢ 
, : 
i ait i 
i ™ 
i oad io “ 
- j 
J 
| 
= 4 § 
i 
=) " } 
7 mrt 





JOHNSON AND YORK. 


1000 W. 800 600 400 





3000 N. 





PLATE XIII, 


200 W. 0 GLOOM SY, 14-00 E. 


are N. 














2400 

















2200 














2800 
—+—42600 
+—424.00 
2200 

| 
2000 





2000 





1800 











1600 














See 1800 














Slime LOO 





1400 








1400 =i 




















1200 





iP 1200 


























1000 














800 














600 














400 


20on, 





600 



































































































1000 
800 
600 
400 
200N. 
eon. 4 
Scale 1:4000 on & 
9 100 200 300 400 SOOFEET | weccrw “Ae! sae ees 540) oe PLA Aas na ; 
ELEVATIONS AND DEPTHS IN FEET 
|} —~|Tide lines (even feet) 
zoos} [J Tide lines (odd feet) eke 2005. 
from] Whart line | 
x tion of range stake wei AY ; c Py. 
400 [x _]t0ce pe rary in aay = TIBOR i \ a f 
EXPERIMENTAL \ } 
rj] Lower limit of Spartina glabra EVOLUTION BS ee 
Papa] Limits of Zostera marina : Ae ene. 


1000 Ww. 800 600 400 





200 W. 0 200E 00 600 800 1000 1200 i400 E. 


Map oF InNER Harpor, CoLp Sprinc Harzsor, SHOWING THE DISTRIBUTION OF THE VASCULAR 
PLaNts OccurRiInG BrEtow THE 10-Foor LeveL, Nor ASSOCIATED WITH) FRESH WATER INLETS 


By Duncan S. Jonnson anD Harztan H. York, 


Sympos, PLANT INDICATED. 
A Ammophila 
At Aster tenuifolius 
Aa Atriplex arenaria 
Ao Atriplex patula 
B Baccharis 
Cc Cakile 
D Distichlis 
Eu Huphorbia polygonifolia 


fy Iva 

J Juncus Gerardi 
im  Lathyrus 

L Limonium 


pd  Plantago decipiens 

pr Polygonum maritimum 
Ry Ruppia 

Sm  Salicornia ambigua 
se  Salicornia europaea 
sd Solidago sempervirens 
Sp Spartina patens 

sj Spergularia 

sy Suaeda 

T Triglochin 

Z Zostera 


The frequency of the symbols 
indicates approximately the abun- 
dance of the species. Only the 
horizontal distribution along the 
beach can be shown with any 
accuracy, owing to the crowding of 
the symbols in many areas. The 
vertical distribution can be learned 
more exactly from the text. 

The general distribution of Zostera 
and Spartina glabra is shown in 
black. In the case of the former 
the abundance of scattered plants 
outside the area of greater density 
is indicated by the proper symbol 
printed in green. 

The distribution of these plants 
on the marsh is shown on Plate XI. 


SEED PLANTS OF UPPER LITTORAL BELT 81 


Spartina patens, but from 480 east on to the east end of the Spit this belt is 
dominated by Salicornia europea, often mixed with numerous bushy plants of 
its relative, S. ambigua. In one place only (620 to 660 east), does the latter 
become abundant enough to really crowd out the more erectly growing S. 
europea. Three or four similar interruptions of the band of Salicornia europea 
near the eastern end of the Spit are due to short patches of Spartina patens or 
Distichlis. At the eastern extremity of the Spit, Sueda and Atriplex patula 
may be mingled with the Salicornia, while at the very tip the Salicornia is 
usually sprinkled thinly over an otherwise comparatively bare sand beach (plates 
Vv and XIII). 

On the Marsh Salicornia europea may in some places be sparsely distributed 
-and in other parts areas of several square meters may be covered to a density 
of 100 plants per square decimeter. Throughout the Marsh it is chiefly confined 
to the margins of the tide-streams, tide-pools, and artificial ditches (100 north 
by 1,150 east at 6.5 to 7.5 feet and 100 south by 900 east). On spots made bare 
by the smothering out of Spartina patens by tide-trash, Salicornia europea is 
often the first thing to appear when this trash is finally removed by some very 
high tide, e. g., at 100 north by 1,090 east in 1909. On locally elevated areas in 
the midst of the Spartina glabra, even down to the 6-foot level, Salicornia is 
sparingly mixed with such species as Aster subulatus, Atriplex patula, Limo- 
nium carolinianum, and Scirpus nanus, as, e. g., at 400 to 440 south by 770 east, 
between two streams. 

On the east shore of the harbor Salicornia europea is usually seen only at 200 
north, between 6 and 7.5 feet, where it is only sparsely sprinkled among the 
Spartina glabra and the 8. patens on this rather well-drained point of the shore. 
In one season only (1908) were a few scores of this plant found between 7.25 
and 7.75 foot levels, on the stone pier at 950 north. Nota single plant of this 
species could be found along the whole west shore, from the northern edge of the 
Marsh to the Spit, though a careful search was made for it. 

The factors influencing the distribution of this species may best be suggested 
after noting the distribution of the second species of Salicornia, which imme- 
- diately follows. 

Salicornia ambigua in the upper littoral belt: This perennial, half-ever- 
green species of Salicornia is confined to the eastern third of the Spit, except for 
a colony of 5 tufts, each 0.5 meter across, that has established itself on the north 
side of the stone pier on the east side, and a single plant at 1,010 north on the 
same shore. Mature, established plants are readily distinguished from those 
of S. europea, but it is possible that this species may be represented on the 
Marsh by seedlings or young plants which were not distinguished from those of 
the annual species. On the south shore of the Spit S. ambigua is chiefly confined 
to the region between 390 and 600 east (plate x11r), not more than a score of 
plants of this form being found outside these limits. Only between 620 and 660 
east, however, does this Salicornia become completely dominant. Here it forms 
a practically pure stand, with thickly matted branches, over a strip 1.5 meters 
in width, between the 6.25 and 6.75 foot levels (plate xB). Along the beach 
from 390 to 620 east this species is mingled with or at times crowded out by 
S. europea, with now and then a turf of Spartina patens or Distichlis to inter- 
tupt the continuity of the stand of these two glassworts. Beyond 660 east the 
plants of 8. ambigua are either scattered singly or may be grouped in twos and 


82, THE RELATION OF PLANTS TO TIDE-LEVELS 


threes, over a beach covered chiefly, though often sparsely, by either Sueda or 
Salicornia europea. There is one group of a dozen of these perennial Salicor- 
nias between 790 and 820 east, of which most are 6 or 8 dm. across the individual 
plant (plates 11 and XIII). 

The distribution of the two species of Salicornia: From what has been said 
above of the distribution of these two Salicornias, it is evident that the concur- 
rence, in any area, of all the conditions allowing the establishment of a dense 
stand of either is rather rare on the shores of this harbor. Even the thinner 
stands occur in but a few and relatively small areas, except on the Spit. We are 
unable to do more than suggest the possible factors influencing the horizontal 
distribution along the shore. We have been unable to discover any very probable 
determinant of the vertical distribution of these two plants. It seems evident 
that the horizonal extent of the patches of the annual S. europea, along the 
beach, is determined by its perennial competitors, especially by Spartina patens 
and Distichlis. The seedlings of this Salicornia can start only on unoccupied 
soil, which means either soil that has been bared of its competitors or soil that 
can not be successfully occupied by them, even with their advantageous habit 
of spreading to adjoining territory by means of their rhizomes. It will be 
interesting to note in this connection that in early April 1911, when the beach 
was still bare of vegetation after the winter, many seedlings of Salicornia, 
probably S. ewropea, were found on the Spit far beyond the areas that are oc- 
cupied by mature plants in summer. Many of them, for example, were found on 
the mud between the dead stumps of the Spartina glabra, down as far even as the 
5-foot level. Others had started higher up, where they would be sure, later on, 
to be shaded out by the rapidly growing shoots of Spartina patens. 

Shreve, and also Chrysler (Plant Life of Maryland, p. 131 and p. 178), have 
suggested that Salicornia europea grows on areas where the soil-water is subject 
to concentration by evaporation, and that the high salinity so attained is really 
the factor that determines the occurrence of Salicornia on these areas. This 
assumption would not adequately explain the distribution of this species at 
Cold Spring Harbor, for here, as we have seen, it grows luxuriantly on beaches 
the soil of which is flushed out by a submergence of from 3 to 3.5 hours each 
tide. Moreover, S. ewrope@a grows on the point between two streams, at 440 
south by 770 east, just above the 6-foot level, where it must be overflowed by 
fresh water for at least 3 or 4 hours daily. As the tide rises the fresh water of 
the two streams is backed up north of the causeway, and it is not until the tide 
has risen to at least a foot above the substratum that the layer of fresh water 
next the substratum is replaced by salt water. Salinity tests made at this point 
show specific gravities of soil water of from 1.015 to 1.017. It is to be remarked, 
however, that Salicornia has never been found growing where fresh water is 
constantly present in the soil or flowing over it at low tide. 

The Salicornias, at least S. europea, grow on either muddy, sandy, or gravelly 
soil, though the denser stands of both species are found on the gravel. All soils 
bearing either Salicornia have at least moderately good drainage, for example, _ 
when growing near tide-pools it is always on the more elevated parts of their 
margins, above the constant water-level. Salicornia is found in well-lighted 
areas, in the open sunlight, except for the little shade given it in some places by 
the neighboring Spartina glabra. Neither Salicornia has been seen on the west 
side, where the conditions are apparently otherwise favorable, but where, as we 
have seen, these levels of the beach are deeply shaded for half the day. 


SEED PLANTS OF UPPER LITTORAL BELT 83 


The seedlings of Salicornia europea are very numerous in the spring. In 
July each year plants of all sizes are found, from seedlings of 2 or 3 cm. up to 
mature plants. This indicates a marked difference either in time of germina- 
tion or in rate of development, for no seeds have as yet been shed even from the 
oldest plants of the season. The perennial 8. ambigua does not appear to spread 
by the rooting of its decumbent branches, and probably does so by its seeds, 
though its seedlings were not distinguished from those of S. europea. 

The vertical range of distribution of Salicornia europea is from 6.5 to 7.25 
feet, but small plants of it have been found as low as 5.5 feet (200 north 
by 1,020 east), and rarely it goes up to 7.75 feet (2,860 north by 500 east and 
100 south by 900 east). Salicornia ambigua is found only between the 6.5 and 
7 foot levels on the Spit, but may be capable of ranging much more widely where 
conditions encourage a more abundant growth. As a general conclusion from 
all observations made on these Salicornias, it may be suggested that the vertical 
distribution of these plants is determined primarily by physical conditions, of 
which the chief are the time of submergence of the shoot at its lower limit and 
the low percentage of soil-water at its upper limit. The horizontal distribution 
is directly influenced somewhat by soil characters, but is apparently determined 
ultimately, in the case of S. europea at least, by the power of its perennial 
competitors to hold their own against the seedlings of the Salicornia. Between 
the two species themselves there is evidently keen competition. 

Scirpus americanus in the upper litoral belt: This plant, which is a dark- 
green, few-leafed rush with triangular culms, about 0.5 cm. thick, and from 
0.5 to 1 meter high, is widely scattered about the harbor in this belt, except on 
the Spit (plate x11). Along most of the east and west shores where this rush 
occurs at all it is sprinkled in with Spartina glabra near the upper border of the 
latter (plate 1vB). Higher up there is still but a sprinkling among the suc- 
cessors of the Spartina, such as Spartina patens (e. g., 1,000 to 1,020 north by 
1,050 east). In still other places, though the stalks of the Scirpus may be thinly 
scattered, the soil between them may be destitute of other plants and perhaps 
covered with a layer of tide-trash beneath which this plant seems to persist more 
- readily than other species. There are but few places along the west shore where 
this Scirpus is abundant enough to dominate the upper littoral belt (e. g., 
between 640 and 800 north, 900 and 1,000 north, 1,850 and 1,900 north). Only 
on the southern end of the Marsh at the head of the harbor (350 to 500 south by 
1,000 to 1,150 east) do we find this species really dominant over any consider- 
able area (plates XV B, XIX B, and xx A). LHven here it seldom occurs in as pure 
a stand as that formed by Spartina glabra, 8. patens, or even by Sueda and the 
Salicornias on the Spit. The soil occupied chiefly by Scirpus is usually firmly 
bound by its rhizomes, which run about horizontally about 10 to 15 cm. below the 
surface. In the denser stands there are 10 to 15 culms per square decimeter. 

The soil bearing Scirpus americanus is peat or mud, chiefly between the 6 and 
8 foot levels. Sometimes, near the larger rivulets, it gets down to the 5-foot 
level on lumps of peaty mud which are surrounded by fresh water for 4 or 5 
hours at each low tide (1,250 north, on the west shore). It does not grow 
on the gravelly areas from which this peaty top-soil has been eroded by these 
streamlets. On the other hand, this rush may grow at considerably higher 
levels than the upper limit mentioned above. This is true at one or two points 
along the west shore (e. g., 1,700 north), and especially on the marshy area 


84 THE RELATION OF PLANTS TO TIDE-LEVELS 


south of the harbor, where, as noted above, this species attains its best develop- 
ment. Here it grows densely on soil at the 8.5 or 9 foot level, and at one place 
it is found at 9.25 feet. On the sunny east shore at 1,000 and 1,040 north this 
rush forms rather dense patches near the 8-foot level, and ascends still higher 
near the inflowing fresh-water rivulets. 

In the preceding paragraph reference is made to the occurrence of this Scirpus 
near fresh-water streams, and to its complete absence from the Spit, which is 
devoid of fresh water. After studying the entire shore of the harbor, it is clear 
that Scurpus americanus is found only in soils where fresh water is present, 
either running over the surface or barely saturating the mud as the water seeps 
through from little springs in the underlying gravel. This latter seems to be 
the case, for example, on the west shore, near 800 north, 1,800 north, and 
1,900 north, where, though no fresh water is found running over the beach 
between the 7 and 8 foot levels when the tide is out, yet the soil is constantly 
saturated even after many hours exposure. Moreover, the water collected in 
holes dug in this soil is entirely fresh to the taste and, at low tide, fresh water 
is also found trickling out of the beach at the 3 and 4 foot levels, directly below 
these Scirpus areas. On the Marsh also this Scirpus often grows in spots where 
no fresh water is visible on the surface. The soil-water, however, proves to be 
fresh when its specific gravity is taken. This is true, for example, of the large 
area between 400 and 500 south and 900 and 1,100 east, which is dominated by 
S. americanus. The soil-water here is practically fresh during the growing 
season, except just after the very high storm-tides mentioned above. 

In brief summary of the conditions under which Scirpus americanus grows, 
we find that it is a plant of sunny situations. It is absent from shaded soil on 
the west side, though this be wet. In fact, the Spartina glabra from the belt 
below has been found to replace this rush in such wet, shady spots (see p. 45). 
Scirpus grows chiefly on soil between the 6-foot and 8-foot tide levels, except 
on the Marsh and at one or two spots on the east side, where it may reach the 
9-foot level in wet, sunny places. This gives the plants an exposure of 15 or 
16 hours per day in the case of the lower ones and of 24 hours per day for the 
higher ones, except on the 5 or 6 days of each month when high spring or storm 
tides occur. The submergence varies from 3 to 10 hours per day. 

The critical factor determining the lower limit of this Scirpus is probably 
the high salt-content of the soil. It never gets far below the 7-foot level, 
except where fresh water is abundant enough to wash the salt out of the soil. 
It is, of course, possible that this fresh water really acts indirectly, by preventing 
the growth of its competitors in these soils (e. g., of Spartina glabra). It is 
conceivable, for example, that this Scirpus might occupy any soil between the 
5.5 and 8 foot levels, if only its competitors are kept out. This has not as yet 
been experimentally proven. The upper limit of distribution is probably 
determined by shade, or by the lack of sufficient soil-water on some parts of the 
beach. Tlsewhere, on the contrary, even in wet soils, its upper mit seems 
fixed by the competition of other species which can not follow the Scirpus down — 
to levels that are flooded by salt water, but can successfully compete with it when 
they have not this adverse condition to meet. 

Scirpus robustus on the upper littoral beach: This large, more leafy rush 
resembles S. americanus in its distribution, but is less abundant and less widely 


* Tests made at a few points show that this species can grow in soil water with a 
specific gravity of 1.006 or even of 1.017. 


SEED PLANTS OF UPPER LITTORAL BELT 85 


distributed (plates xt and x11). There are but four patches of it on the west 
side and only six on the Marsh, and it is entirely wanting from the east side, 
north of the Marsh, and from the Spit. This species of Scirpus is, in fact, less 
abundant and less widely distributed than several of the other plants of this belt 
to be mentioned later. It is discussed here, immediately after S. americanus, 
for the sake of more ready comparison with this species. S. robustus is con- 
fined, like its relative, to areas with fresh soil-water. It rarely forms pure stands 
of any considerable extent. Stands of 50 square meters are found at 1,600 north 
on the west side, and one near 500 south by 880 east. Nearly pure stands of 
smaller area are present at 590 south by 740 east and near 120 south by 1,200 
east. More often it is mingled with Spartina glabra, S. patens, or Scirpus 
americanus; e. g., on the west shore at 1,980 to 2,020 north or on the Marsh at 
550 south by 730 east. The lowest level from which this species has been 
recorded is 7 feet and its upper limit is at 9 or 9.25 feet. As was suggested 
above, this Scirpus is found only on soils supplied with fresh water. In some 
areas this water is evident on the surface, e. g., on the west side at 1,415 north, 
on the Marsh at 120 south by 1,200 east. In other places the fresh water is not 
at first evident, but is found on investigation to be present in the soil. A striking 
instance of the latter sort is the small area, between two streams at 470 south by 
830 east, which is elevated 1.5 or 2 feet above the bed of these streams. ‘his 
area is covered with a mixture of Spartina glabra, 8. patens, Scirpus americanus, 
and, most prominent of all, the present species. ‘This same mixture extends 
eastward from the point named on soil, from 8 or 10 inches below the surface, 
of which a rivulet of fresh water trickles out at low tide. Not only is the soil- 
water fresh, but the overlying water at high tide never becomes very salt. Spe- 
cific-gravity tests made at this point when the tide was at the 8-foot level showed 
a density of but 1.005 at the surface of the soil bearing these plants. At the 
time of the spring tides, which in summer reach 9 feet, or of storm tides, which 
in summer reach 10 feet and in winter even 12 feet, all inflowing fresh water 
must be backed up south of the road embankment, which crosses the Creek. The 
whole Marsh would then be covered with from 1 to 3 feet of sea-water with a 
density of 1.019, like that of the harbor itself. This shows that the shoots and 
more superficial roots and rhizomes of this plant can endure submergence in salt 
water for several hours a day, even when in a growing condition. It is probable, 
however, that the salt water never penetrates far into the soil here, because of 
its compactness and of the constant supply of fresh water from below. 
Distichlis spicata on the upper littoral belt: This is a slender grass 4 or 5 
dim. in height, with narrow, often glaucous leaves. It grows, chiefly between the 
6.5 and %.5 foot tide-lines, in a number of small areas on the Spit, at a few 
points on the Marsh, at one point on the east side, and two on the west shore 
(plates v, x1, and x1v). Pure, or nearly pure, stands of Distichlis are found 
at a few points on the Spit (plate xx B). These are but a few meters long each, 
but 6 or 8 dm. wide, and all are near the 7-foot tide level (e. g., 500 east at 7.75 
feet, 580 to 590 east at 6.5 to 7.5 feet, and 800 to 820 east at 6.5 to 7.5 feet). 
On the Marsh similar dense growths of Distichlis, over smaller areas, are found 
at 0 north by 940 east at the 7.25-foot level, and at 370 south by 820 east near 
”.5 feet. Elsewhere about the harbor Distichlis is mingled with Spartina 
patens, as at several points on the Spit (950 east, 800 to 1,000 west), on the 


86 THE RELATION OF PLANTS TO TIDE-LEVELS 


west shore (800 to 930 north, 1,600 north), on the east side on the pier (950 
north), and finally on several small areas of the Marsh (e. g., 0 south by 1,200 
east). In other areas where Distichlis is still dominant, there may be a large 
admixture of Sueda or Salicornia, or even a scattering of Atriplex arenaria 
(e. g., 2,700 north by 0 east, 2,850 north by 800 east). 

The soil on which Distichlis grows is a partially drained, peaty muck, occa- 
sionally mixed with sand, as, for example, at the western end of the Spit. More 
rarely this grass is found in comparatively fine sand, in which on the Spit (750 
east) it gets up above the 8-foot level. Nowhere about this harbor was Distichlis 
found growing in the shade or in soil wet with fresh water. The latter fact may, 
of course, indicate that the fresh water is directly injurious, or perhaps we 
should say that the semidiurnal alternation of fresh and salt water is unendur- 
able. Or on the other hand, its absence from wet areas may mean that it meets 
other competitors, or meets some of its usual competitors at a greater disadvan- 
tage on wet soils. ‘This grass lives on soils of quite varied character, taking all 
sides of the harbor into account, which indicates that it could occupy many 
other areas than at present if it were not for its competitors. In fact, then, it 
seems clear that the chief influence determining the limits of the Distichlis in a 
horizontal direction along the beach is the competition of its neighbors. 

It is difficult to discover what external condition fixes the lower limit of 
Distichlis at 6.5 feet. It may be that the shoot will not endure a submergence 
of more than 2 or 3 hours each tide or that the rhizome can not withstand sub- 
mergence longer than 3 or 4 hours per tide. On the other hand, it may well be 
that it can not compete successfully with Spartina glabra, with which it is 
nearly always in contact at its lower margin. The upper limit of this grass is 
quite variable, but it has proven impossible to determine whether this is fixed 
directly by some character of the soil, such as the water-content, or by the com- 
peting plants there present. 

It is, of course, realized, as has been mentioned in other cases, that the 
particular conditions which limit the distribution of any species can not be 
determined by field observation alone, but that resort to experimental study will 
be necessary to do this with certainty. At the start, however, field observation 
must be relied on to indicate the possible factors from among which the experi- 
menter may hope to select the actual controlling factor or factors. The sug- 
gestions offered in connection with most species in this paper are not made in 
the belief that they are finally established as causes of the distribution found, 
but as suggestions likely to prove useful to the experimental investigator. 

The distribution of the nine other species of angiosperms found in this belt, 
but which seldom dominate any area above a few square decimeters in extent, 
may now be briefly indicated, taking them up in alphabetical order. 

Atriplex arenaria: This hoary-leafed annual is found very sparsely scattered 
on the eastern half of the Spit (plates v and xiv), on the Marsh (plates xz and 
XII1), and on the old pier at 950 north on the east shore. Its usual range is from 
the 7-foot to the 8-foot levels, though its extreme range is from 6.25 to 8.75 feet. . 
It occurs in rather sandy soil on the Spit, but is most frequent in the turf of 
Spartina patens along the edges of the tide-streams and. ditches on the Marsh. 

Atriplex patula hastata is, in most years, very much more abundant than A. 
arenaria. It is also more widely distributed about the harbor and has a greater 
vertical range (plates v, x1, and x11). This species has been recorded on the 


SEED PLANTS OF UPPER LITTORAL BELT 87 


east side of the harbor at 320 north (about 10 clumps, in 1912), and at 400 to 
480 north whenever fresh water is absent. The densest group about the harbor 
was found on the pier at 950 north by 970 east, where there were 150 plants in 
1912. On the south side of the harbor this plant is usually distributed rather 
sparsely over most of the area of the Marsh. It grows here chiefly between the 
7-foot and 8.25-foot tide-levels, is most frequently associated with Spartina 
patens, and is oftenest found on the better-drained soil at the edges of tide-pools, 
streams, or ditches. Its general frequency is that indicated on the area mapped 
in plate vir. On the west side this species is sparsely but widely distributed 
along the whole natural shore (740 north, 1,200 to 1,410 north, 1,650 to 1,750 
north and 1,970 to 2,070 north). Usually it is found among Spartina patens, 
but it is sometimes mingled with Solidago sempervirens near the 8-foot level, 
and it is absent from soils saturated with fresh water. On the south side of the 
Spit, Atriplex patula has the same wide but sparse distribution that we have 
noted elsewhere. It is found scattered in the dense turfs of S. patens (800 to 
1,000 west), or close to the upper margin of S. glabra (840 east at 6.5 feet). 
The more usual range of this Atriplex is from 6.5 to 7.5 feet, but at 400 to 480 
north on the eastern shore it gets down below 6 feet, while on the well-drained 
shore at 320 north on the east side, it goes above 8 feet. On the west shore, near 
1,800 north, and on the north shore of the Spit, between 400 east and 400 west, 
it is often found at 8.5 feet. 

Iris versicolor, while really to be regarded as a denizen of the next higher belt, 
may form dense clumps of vigorous, abundantly fruiting plants in the upper 
littoral belt, on firm soil that is protected by neighboring springs and rivulets 
from saturation by salt water (plates 1vB and x11). Thus, on the west shore 
(1,350 north, 1,400 north) Jris gets down to 8 feet or just below, while on the 
east shore it grows in soil at 7.5 feet, or even, at one point, at 7 feet. In the 
latter locality (10 north by 1,192 east) the soil-water at this level, and the sap 
of the Jris roots growing in it, are not at all salt to the taste. The soil, however, 
is covered with salt water twice daily, except during two or three neap tides of 
each fortnight. Jris forms a very striking example of the way in which the 
shoots of some inland plants can withstand immersion in salt water, if only the 
soil-water be fresh. The general occurrence of this species about the harbor is 
indicated on plate x11 and will be discussed in speaking of the vegetation of the 
next higher belt. 

Linonium carolinianum is one of the most widely distributed species of this 
upper littoral belt in soils free from the influence of fresh water. ‘This has often 
been suggested above in speaking incidentally of its occurrence in stands of 
other species. It is a broad-leafed, thick-rooted perennial found on all four 
sides of the harbor. On the east side there is a bare sprinkling of it in the 
better-drained spots from 20 to 450 north and from 960 to 1,150 north, while 
between 800 and 900 north, at 7.75 to 8 feet, there were 30 plants in 1912. 
Finally, on the pier at 950 north, is found the densest and most extensive stand 
about the harbor. There are over 300 plants around the border of this wharf, 
and where densest there are 20 plants per square meter. 

On the Marsh, Limonium occurs chiefly along the northern border between 
6.5 and 7 feet, usually bordering tide-pools, tide-streams, and ditches (0 north 
by 880 east), and also on certain artificial, gravelly elevations (10 south by 
800 east). The total number of plants on the Marsh is not over 150 or 200, 


88 THE RELATION OF PLANTS TO TIDE-LEVELS 


and the general scattered distribution of the plant is indicated by that shown for 
a typical area on plate VII B. 

On the west shore Limonium has been found at only three points, all of which 
are artificially gravelly areas. A few plants are at 750 north, on a dilapidated 
boat-landing. About a dozen specimens were found at 1,070 north and the 
same number at 2,090 north. 

At the Spit, Zimonium is most abundant on the western quarter of the south 
shore (plates v, X B, XII, and xv). In the broad band of Spartina patens here 
between 700 and 900 north several dozens of this species are scattered, sometimes 
4 or 5 ina square meter. On the eastern half of the Spit, Lamonium is scattered 
very sparsely; ¢. g., only 10 plants were found between 0 and 260 east. Beyond 
this, eastward to 840 east, the plants may be locally somewhat more abundant, 
but on the whole they are evenly scattered, and not more than 100 plants are 
present altogether on this half. 

The large majority of the plants of Iimonium about the whole harbor are 
found between the 6.75 and 7.75 foot levels. On well-drained peaty soil, such 
as turfs of Spartina patens, Limonium may get down to 6.5 feet, while on hard, 
gravelly beaches, out of reach of fresh water, it may go up to 8 or, in one 
instance, to 8.25 feet. It is found only in sunny situations. 

Plantago decipiens on the upper littoral belt: This narrow-leafed fleshy 
perennial is found in this belt at three or four points about the head of the 
harbor, on gravelly or half-drained peaty soils between the 6.25 and 8.25 foot 
levels (160 south by 1,090 east, 400 to 480 north by 1,040 east, and 20 south 
by 730 east, etc.) (plate x11). It is rather surprising that this plant has not 
been seen on some of the gravelly beaches of the Spit and west side of the harbor, 
unless it be the abundance of fresh water in the latter case and perhaps the poor 
drainage of the former, due to humus packed between the pebbles. 

Samolus has been seen at but one point in the upper littoral belt (200 north 
- by 1,050 east), where it grows between the 7.5 and 8.25 foot levels associated 
with Juncus Gerardi and Salicornia, and near its upper limit bordered by 
Teucrium canadense and Psedera quinquefolia. 

Scirpus nanus is a diminutive species that occurs in the upper littoral belt 
somewhat more abundantly than either of the last two species. It usually forms 
dense turfs, sometimes a meter or more square (122 south by 1,089 east), and 
grows on fine-grained peaty soils that are often bare, or nearly bare, of other 
vegetation, except alew such as Rhizoclonium and Vaucheria (plates xx1 and 
xx11). The seed plants most often found with this Scirpus, when any are 
present, are Salicornia europea, Distichlis, Atriplex patula, and occasionally 
Spartina glabra. Scirpus nanus is confined to a half dozen locations on the 
Marsh (e. g., 500 south by 700 east, 25 north by 1,100 east), one area on the east 
shore near the mill (400 to 480 north), and two areas on the west shore (660 
north at 7.5 feet and 850 north at 7 feet). The soil on which this plant grows 
is always pretty completely saturated with salt water, the fine texture of the soil 
enabling it to hold the water well from one high tide to the next. At 6 south by 
1,050 east, at 7.33 feet, this plant was growing well at the margin of a tide-pool, 
the surface of which, for the purpose of killing mosquito larvee, had been kept 
covered during the summer with crude petroleum. The Scirpus we are discuss- 
ing occurs chiefly in sunny spots, and between 6.5 and 7.5 feet, although it has 
been found as low as 6.25 and as high as 8 feet. 


PLATE XIV, 


oft. Btt. 2850N cog 






































































































































































































































PLATE XIV, 
JOHNSON AND YORK. 
2800 2850N 
2700 50E 
6 ft. Tat 8ft. 9 ft. 
PA gh VO © en tig PPP : : 
55% Oo, o 2®o a QD » : 5 P 
: ‘o8f... ol ® # @ PoP oe : 
o®\o. ort oo, eerie ) 
°90\° “o: | o Fine 25-5 
,ooO"1, o: 3 (3) 
cy Mere a 0 et eee ee ee Bee 
{ DOH 3) > 2 
oO Qyo o > 
oo? a (00) \ 4 > 
cole 0 \® y H>? z 
@ MO)O°. 07} © et eee eS Soe) A [ac | ee SO Me Se OE GE ee ee es ps a eee ee ce 
\ "08 ae eS e ») 
‘ C7 CD) CE) gry) s\n EL) JE SO) NN ede eS Se a a ee ee ee ee 
\ %00)° so: @ eee a 5S @ : = 
Ree (a Ob. cov) ip oe a i a a a re ea ee ee 
52) . : 0) av) 
o2\° 20 PH Se Ne eee Ye eS SS es ey come Vee eee 
iy as ae ® 
: Os i 5 00) Ds en Ves. 5 ae iin ae ars MN MMe ea ee een ye ce ise or A an Ne eee 
ee 6 O¢: Od \ vi Pages es 
cagjeeee hg g Do ete se et ee eee Ne ee 
sg 3.00 B Je A HoH 
» oO eS a DP Ts abs ae eg a eee) ML aa eG Fa eae ag SP a ee yh li Ra meen Onn aa ON 7)! ein oe 
“OLOe® abe I Me (i 
GAP DH . Oz !@ 9 @ wa A DNC ee Ne a ee pe el AG tte leslie |e etfs Nera 
-D8o0r.0 - So 2 AnPe 
> .09 ‘loo © OA 
a OM 7 oe E és Q Eo P 
d0%C ob?’ “ p's Fag ae G28 ane he eo oe a) ee ee ae a 
= OF) ONG: Oo , A fe} (a0) 2 4 
ap? @ “d. a Be A o aN ray BO Re ee ee 8 Se SS ee Ee ee eS 
O,000(9 oo @ - Ate ee eS ee SS Oe eee 
Soo: *\O- A Yee ll ccuey le. ies ele ER La ie ee a Sa i re a 
Hor cae A d Se a eS ee eee a ee eee ee ee et es ee ee ee 
ny ail! 4 so P 
OWCO.e An ii Oe 
-O O° A oy WE 
Ee Sp A P 
oO m0) Dip. Ge i (couse ae ae ae ce EE acer = Ee ae ae ey et Nee ph cen i eee ey ene ee — yee a ee a 
So) GOs. -. Pe = 
~ 2M = a0 : Oy = » (ee 2 SSS aa | = SS gion (ae aoe oe oe er ae = Pe ae eeee re Cee oer Miia <r 
efecto Se eS SS eS 
z ; © 
OF OEE tag ee en is | © Me ee te ee ee Sp ee Ee an ea Saar Sas go 
orate 
OO) eno re NN a aN a ae ee cee agp emer «eae yg, ey ye mere eng ghee nm Wee een ka een oe 
toe 
Sy ee 
- 9 “5 ® 
Pc eh ic S/S ee Se ee ee ee 
an 7 BF. 


2800 N 
50 Feet 


Beitr TRANSECT OF SPIT, SHOWING DiIsTRIBUTION OF PLANTS IN RELATION TO TIDE-LEVELS ON SELECTED AREA, BETWEEN 
50 anp 100 Fret Hast, 1n Aucust, 1909. 


Every plant is located except for dominant or subdominant species. 
Salicornia europea and Sueda maritima at the margin of the Spartina zone, Ammophila arenaria and Poa compressa. 


By H. S. Conarp anp P. M. CoLtins. 


ScALE 1 ro 150. 


The exceptions are: Spartina glabra in its zone of dominance, 
The boundaries 


of the zones of Spartina glabra and of Ammophila arenaria are shown by a heavy wavy line. Abbreviations and conventional signs used 


are as follows: 


A = Asparagus officinalis. 
B= Oenothera biennis. 


E = Euphorbia polygonifolia. 


F= Cyperus filiculmis. 
H = Chenopodium album. 
K = Polygonella articulata, 


L = Limonium ecarolinianum. 


M = Ambrosia artemisicefolia. 
N= Xanthium echinatum. 
P= Panicum sp. 

Q = Quercus sp. 

R= Spartina patens. 

S = Salsola kali. 


T = Taraxacum officinale. 
V = Lactuca sp. 


Spartina glabra alterniflora. 
Ammophila arenaria. 


1¥1== Poa conupressa. 
)= Cakile edentula. 


© = Salicornia europea. 

@M = Sueda maritima. 

@ = Solidago sempervirens. 
* = Ailanthus glandulosa. 
A = Distichlis spicata. 
LJ= Atriplex patula hastata 
N= Atriplex arenaria. 





SEED PLANTS OF UPPER LITTORAL BELT 89 


Spergularia marina is a fleshy annual occurring in this upper littoral belt, 
which has been found during most summers in a half a dozen locations on the 
Marsh, in two areas on the eastern shore, and in two or three areas on the west 
side (plate x11). It has not been recorded from the Spit. The areas mentioned 
on the east side are on the well-drained top of the old stone wharf (950 north at 
? to 7.5 feet) where scores of plants were found in 1912, and a stretch of beach 
between 300 and 470 north, along the whole of which only 40 or 50 plants were 
found, some of them near fresh-water rivulets, but not where the soil could be 
really saturated with fresh water. The four areas at which Sperqularia has been 
found on the western shore are 1,020 north at 7 to 7.5 feet, 1,210 north at 7.75 
feet, 1,400 north at 7 feet, and 2,090 north at 8 feet. ‘Two of these are in the 
neighborhood of fresh-water streamlets, though not where the soil can be satu- 
rated with the water from them. It is possible that these streamlets favor the 
Spergularia only as they allow better drainage of the soil on which it grows by 
cutting channels through this peat clear down to the underlying gravel. The 
second and fourth areas cited for the west side are far larger and more densely 
covered. There are 10 sq. meters dominated by Spergularia at 2,090 north. On 
the Marsh, the highest plant, a single one, was near the 8.75-foot level (298 south 
by 1,075 east). More commonly it was found between the 6.5 and 8 foot levels. 
It occurs in dozens near 90 south by 1,080 east, and also by the edge of the 
tide-stream near 100 south by 1,150 east at 6.5 to 7 feet. Still more numerous 
plants were found on mud covered chiefly by mats of alge, and with but a few 
other scattered seed plants, e. g., 10 plants nearly covered a spot 2 meters 
across at 20 north by 780 east in 1912. Several square meters of soil beneath a 
bath-house at 20 south by 740 east were thickly carpeted with Spergularta in 
1912. The most surprising habitat on which a group grew was an undermined 
block of marsh turf, 1 meter broad and 2 long, that had fallen from the east bank 
of the Creek, at 150 south by 790 east. This block had probably fallen off 6 
months before our observations began, and the plants on it continued to grow 
well all summer. On the surface of this turf there grew not only the Spartina 
patens, which had held sway over it when in place on the Marsh, but Atriplez, 
Salicornia, and several other seed plants, among them Spergularia. While our 
observations are not complete enough to establish this conclusion, it is suspected 
that the bettter drainage, from the exposure of five surfaces of this block, 
instead of one surface, as when it was in situ in the Marsh, made it possible for 
the plants on it to persist there. At the middle level of this block (4 feet) these 
plants were exposed only 6 hours per tide instead of for 9.5 hours, which was 
its exposure when the block was in situ on the Marsh at 6.5 feet. On the other 
hand, the time of submergence was doubled, being increased from 3 hours at 6.5 
feet to over 6 hours at 4 feet. 

Triglochin maritima has been found in the upper littoral belt only on the 
Marsh and the adjoining portion of the eastern shore of the harbor south of the 
mill (plate x111). It is a small perennial having the habit of Plantago mari- 
tima, being rather thinly sprinkled—a dozen or two plants—among the Spartina 
patens (160 south by 1,075 east and 0 north by 740 east). In other places it is 
scattered among Solidago sempervirens (350 north by 1,000 east), or on gravelly 
beaches free of Spartina glabra (400 to 450 north by 1,060 east). T'riglochin 
grows on rather poorly drained muck-like soils, out of reach of fresh water, 
between the 6 and 7% foot tide-levels, with the exception of one colony on the 
Marsh that is growing above the 8-foot level. 


90 THE RELATION OF PLANTS TO TIDE-LEVELS 


The only other seed plants found in this upper littoral belt are the occasional 
inwanderers from the belt above. These are plants that are really characteristic 
of the higher belt and only push down below the boundary where the soil 
conditions are unusual, e. g., where it is either gravelly and well-drained, or 
where it is constantly saturated with fresh water. The most important of these 
wanderers from the upper belt is Solidago sempervirens, of which mature bloom- 
ing plants have been seen between 7.5 and 8 feet, and seedlings with leaves 1 dm. 
long have been seen at 6.5, and a few even at 6 feet. But the vast majority of 
plants of this species grow above the 8-foot tide-line. Jris versicolor, which we 
have included as an inhabitant of the upper littoral belt, is also a plant more 
characteristic of higher levels, but, probably because above the 8-foot level about 
this harbor there is more competition and often dense shade, on the springy 
shores that would suit Jris, the majority of plants of this species are found at 
or just below the 8-foot tide-line. 


B. ALG! OF THE UPPER LITTORAL BELT. 


We have already seen that the firm beach and the marshy shore between the 
6.5 and 8 foot levels are inhabited in common by a considerable number of 
seed plants. In fact, all but three or four of the species that may become 
dominant between these levels are found on both types of shore. 

Essentially the same thing is true of the alge of this belt. Out of more than 
30 species recorded from this upper littoral shore and the wharves at this level 
12 may be regarded as dominants, over larger or smaller areas, between seed 
plants on the shores, or on stones and logs of the wharves. These plants are: 
Anabena torulosa, Calothriz crustacea, C. fusco violacea, Enteromorpha clath- 
rata, Lyngbya estuaru, L. semiplena, Microcoleus chthonoplastes, M. tenerri- 
mus, Monostroma latissimum, Rhizoclonium riparium, R. tortuosum, Vaucheria 
thuretu. Any one of these 12 species may grow more or less by itself, or, 

commonly, in admixture with one, two, or more other species forming tangles, 
_ felts, or incrustations. These mixtures, where seed plants are for any reason 
absent or sparse, may form coatings over the surface of mud, sand, pebbles, or 
living or dead parts of the larger plants. These tangles or felts or crusts are 
found dominating shore areas of from a few square centimeters to many deci- 
meters, or rarely of several square meters, in extent. 

Of the 21 other species of alge found in this belt, some may form small and 
infrequent tufts, globules, or coatings, but most are scattered more or less 
sparsely through the felts and incrustations made up chiefly of one or several of 
the 12 dominant species mentioned above. Most of these 21 species, like the 12 
dominant ones, have been recorded from both beach and Marsh, which indicates 
their pretty general horizontal distribution about this belt. The distribution 
of the alge is in this respect comparable with that of the seed plants mentioned 
above, and helps to give its character to this belt. These 21 less common 
species of alge recorded for the upper littoral belt are the following: 
Amphithria violacee (Kitz), Anabena variabtlis, Calothriz pulvinata, C. 
scopulorum, Lamprocystis roseopersicina, Isactis plana, Lyngbya lutea, Nostoc 
spp., Oscillatoria sp., Polycystis elabens, Rivularia plicata, Rivularia sp., 
Spirulina tenuissima, Cladophora expansa, Hnteromorpha intestinalis, Ilea 
fulvescens, Ulothria (impleza?), Ascophyllum nodosum, Fucus vesiculosus, 
Bostrychia rwularis, Hildenbrandia prototypus. 


ALG OF UPPER LITTORAL BELT 91 


From the two lists just given it will be seen that, aside from Ascophyllum, 
Fucus, or Bostrychia, in occasional tufts and Hildenbrandia incrusting the 
pebbles of fresh-water streams, the alge of this belt are Schizophycee or 
Chlorophycee. 

The felts and mats of alge found on the upper littoral levels of the Marsh 
and those of the west shore, though similar in general character, are somewhat 
different in make-up, and, in the commoner constituent species, from the felts 
and coats of the sandy shore of the Spit. On the soft and constantly wet mud, 
on the bases of seed plants growing on the Marsh, and on many wet spots on 
the west shore, the alge form in some places loose dark or light green turfs or 
mats, composed usually of several species. In other places green or gelatinous 
blackish blots occur which are often made up of a single species, nearly pure. 
On the sandy or gravelly better-drained beaches of the Spit, though loose mats 
are not entirely wanting, the alge present are more often arranged in dense felts 
over the firm mud or sand and in the furrows between the pebbles. Others may 
form compact leathery or slightly spongy, dull blackish incrustations over the 
projecting surfaces of the pebbles of the beach (plate xB). The first type of 
association, the tangles or felts on sand or mud, are scattered quite generally 
along the whole south shore of the Spit, between the 6-foot and 7.5 or 8 foot 
levels, but chiefly between 6.5 and 7 feet. On sunny days, the firmer of these 
felts on the more sandy mud of the beach dry out and crack into numerous small 
polygonal sheets, several centimeters across and a millimeter thick. These curl 
up at the edges and may peel off sufficiently from the substratum to be floated 
to a new locality at the rise of the tide. Associations of the second type referred 
to, the dense incrustations on pebbles, or more rarely on shells, simply dry, 
during low tide, to thin, hard coats, adhering tenaciously to the surfaces of the 
pebbles. The tangles or mats found about the bases of the seed plants of this 
shore are looser and more like those found on the Marsh and on the west shore. 
These dry out to curly or cobweb-like tangles hanging loosely about the stems of 
their supports. 

The distribution of the tangles, turfs, felts, and crusts of alge on the Spit 
has been fairly constant during the several years our study has been in progress. 
Detailed notes made in 1908 and 1910 show essentially the same distribution of 
the various types of association of the alge of this belt. It is as follows: 
Beginning at 1,000 west we find rather sparse loose felts on sandy mud beside 
the footpath among Spartina patens, etc., at 7.5 to 7.75 feet. These felts are 
made up chiefly of Lyngbya, Microcoleus, and Oscillaria, but with considerable 
Rhizoclonium and some Vaucheria. From here on eastward to 800 west, we 
find the soil covered with a thin felt from which Rhizoclonium and Vaucheria 
have about disappeared, while Calothrix is more abundant than farther west, 
forming a blackish coat on pebbles. From this point eastward to 670 west, 
the felt is sparse, and chiefly of Lyngbya, Microcoleus, and some Rhizoclonium 
near the 6.5-foot level. From 670 west eastward to 560 west there is a con- 
siderably denser felt, chiefly of these same Schizophycez, on the soil of the areas 
dominated by Salicornia and Sueda, and certain intermittent areas of the 
pebbly beach have black incrustations of Calothriz, etc. From 560 west to 430 
west thin felts of these same Cyanophycee are found only on shaded soil between 
6.25 and 7 feet, and crusts occur on the sides of some pebbles in the shade of 
Sueda or Spartina. Rhizoclonium is found here but infrequently at these 


92 THE RELATION OF PLANTS TO TIDE-LEVELS 


higher levels, and is not wanting from among the Spartina glabra at slightly 
lower levels. Eastward of 430 west to 150 east the algal felts and crusts are 
wanting over most of the loose, gravelly beach. Only where the soil is bound 
together by clumps of Spartina patens do we find small bits of loose alga felts 
on the bases and dead leaves of this grass. From 150 east to 580 east, between 
6.25 and 7 feet, there is a green or blackish felt or crust over all unoccupied mud, 
sand, pebbles, or bits of stubble of Spartina patens and Salicornia europea. 
Not merely are the edges of the pebbles incrusted but the tops of those 4 or 5 
em. across are completely covered. The composition of these felts, which are 
best developed on the Spit, includes the following species: Calothrix (2 spe- 
cies), Lyngbya (38 species), Microcoleus (2 species), Osculatoria (2 species), 
Pleurosigma, Enteromorpha, Rhizoclonium (2 species), Vaucheria, and occa- 
sionally Jlea. Eastward from 580 east to 870 east the coating of alge over the 
soil becomes rapidly sparser and, before reaching the latter point, it disappears 
altogether. Some Calothriz, Lyngbya, and Rhizoclonium may still occur on 
the stalks and dead leaves of Spartina glabra, and rarely on the Salicornia or 
Sueda at higher levels (plate vir). 

The distribution of the felts or tangles of algz on the east and west shores 
and on the Marsh is likewise quite constant and similar in different parts of the 
shore-line, except where affected by fresh water or flood-trash. Only on the 
stone pier at 950 north by 975 east is there any considerable development of 
the dense incrustations found so generally on the south shore of the Spit. On 
the gravelly top of this pier, at 7 to 7.5 feet, the pebbles, especially of the 
northern half, are incrusted by blackish mixtures of alge. On the north or 
shaded side of the little mound of soil about each tuft of Spartina patens, velvety 
layers of Calothriz may cover many square centimeters, and in a few instances 
spread over 1 or 2 dm. 

Green or reddish crusts may occur along other parts of both east and west 
shores, on pebbles over which fresh water is flowing. These are made up of green 
unicellular alge, of brownish Ralfsia ? or the red Hildenbrandia. In the tide- 
pools of the Marsh lying between the 7 and 8 foot levels, we find a still different 
type of association of alge. ‘These alge are chiefly species of Lamprocystis, 
Lyngbya, and Oscillatoria, the two latter of which are woven into very firm 
felts 3 or 4 mm. thick, when moist, and often 2 or 3 sq. meters in extent. These 
felts may be partially floated and partially submerged at high water, and either 
hie on the muddy bottom or be supported by sticks and stubble at low water. 
These felts are very well developed even in tide-pools that are frequently sprayed 
with crude petroleum to kill mosquito larve. New and quite extensive patches 
of algal felts, especially of Vaucheria and Lyngbya, may appear in areas denuded 
of the normal covering of Spartina or Juncus Gerardi. They are often formed 
by masses of flood-trash. The alge may dominate these areas for a season or 
two, but are usually driven out by the reinvasion of the region by the grass or 
rush. 

We may now take up, in systematic sequence, the thirty-odd species of alge 
growing in this belt, indicating briefly the habit and general distribution of 
each species, taking up the genera of each class in alphabetical order. The dis- 
tribution of the more important species is indicated on plates vi1I and Ix. 


PLATE XV 





A. Looking over Marsh at High Tide, from the Causeway at 900 East, toward 
2,000 North X< 1,000 East. 





B. Looking over Creek and Marsh at Low Tide, from the Causeway, at 850 East, 
toward 1,000 North * 400 West, showing Spartina patens (at right), Scirpus 
americanus (middle foreground), Distichlis (left foreground), Spartina 
glabra alternifiora (mid-foreground and across middle distance). 


- 


pk 
Ang 


sats ots 


err 4 ew 
ye laa 


La em = 





ALG OF UPPER LITTORAL BELT 93 


THE SCHIZOPHYCER. 

To this class belong two-thirds of all the algee appearing in this belt, as may 
be seen from the two lists on page 90. 

Amphithriz is found on stones in fresh-water rivulets near the lower limits 
of the present belt, as at 1,000 north on the east side. 

Anabena torulosa Lagerh. (Spherogyza carmicheli of Farlow 1881) is, as we 
have seen, more abundant and widespread in the mid-littoral belt. Its 
blackish-green circular patches, however, are not infrequently found between 
the 6.5 and 7 foot levels, especially on mud beside fresh-water rivulets, occupied 
chiefly by Scirpus americanus (e. g., 1,240 north by 575 west). 

Anabena variabilis is a second species that has been found among felted 
threads of Lyngbya at the 7-foot level, e. g., at 1,720 north on the west side. 

Calothriz crustacea is usually the most important constituent of the denser 
felts and incrustations of alge which occur on the south shore of the Spit, espe- 
cially between 560 and 670 west, and 150 and 580 east. These felts are usually 
found at one or two points each on the east and west shores, e. g., 950 north by 
970 east. The most abundant associates of this Calothria in these felts are 
Lyngbya semiplena, Microcoleus chthonoplastes, Rhizoclonium, and Vaucheria. 
The Calothriz is found most frequently between the 6.5 and 7.5 foot levels, and 
on the compact, rather moist soil of a footpath along the Spit, where it is 
partially shaded by seed plants. It is not found near the fresh-water rivulets. 

Calothrix fusco violacea occurs on the stones of wharves, on the Marsh, and 
on soil and pebbles on both the east and west sides of the harbor at 6.5 to 7.5 
feet (950 north by 975 east; 1,060 north by 450 west). It forms dark greenish 
patches of several square centimeters in extent. 

Calothria pulvinata is a species that forms honey-comb-like spongy coats of 
2 to 3 mm. thickness over sandy soil (950 north by 975 east), or on piles and 
logs of wharves (2,300 north by 1,300 east; 1,060 north by 450 west). It is 
found at higher levels than the other species of Calothriz, being recorded only 
from between the 7 and 8 foot levels. 

Calothriz scopulorum is a fourth species of this genus, and is less abundant 
than C. crustacea. It occurs as a dense black felt, nearly a millimeter thick, on 
pebbles or very compact soil. 

Lamprocystis roseopersicina (Cohn) occurs in a few warm tide-pools on the 
Marsh, e. g., at 0 south by 1,005 east at 7.33 feet. It forms a thin, light purplish 
coating over the soft mud, pebbles, or decaying plants in the bottom of the pool. 
It was found only in places where it would be constantly covered, or at least on 
substrata that are constantly saturated with salt or brackish water. In April 
1911 very little of the Lamprocystis was found, and this was confined to narrow 
bands about the lateral surfaces of pebbles just above the surface of the mud in 
which they were partially embedded. 

Isactis plana is occasionally found in this belt, forming close felts or incrusta- 
tions over the mud or pebbles, very similar to the more abundant ones of 
Calothriz. 

The genus Lyngbya is represented in this zone by L. estuarit, L. lutea, L. 
semtplena, and three or four other less abundant species, which have not been 
identified. Of these, L. estuarit, the occurrence of which at lower levels we have 
noted, is the most important because of its more general distribution and its 
abundance. About the borders of the Marsh south of the harbor, L. estuart is 


94 THE RELATION OF PLANTS TO TIDE-LEVELS 


a principal constituent of the felts over the surface of the mud, among the 
Spartina patens plants, up to 7 feet (e. g., 25 north by 800 east). Along the 
west shore L. estuarw gets up to the 7-foot level among Spartina glabra in 
places where the soil is kept barely damp by seepage of water from the shore 
(1,800 north by 820 west, etc.). On the Sandspit, L. wstuarw is rarely found 
above the 6.5-foot level (500 east), though, as we have seen, it is present just 
below this level. 

Lyngbya lutea is a chief constituent of rather firm felts occurring on wharves 
and beaches of the west shore. It is found in patches of a few square centi- 
meters in area, up as high as the 7-foot level. This species is also present 
sparingly at lower levels down to 3 feet. 

Lyngbya semiplena and several other smaller species are frequently found 
together with L. estuarvi and its associates about the borders of the Marsh, and 
also less frequently on the shore of the Spit. L. semiplena is the most abundant 
and widespread of all the Cyanophycee on the Marsh. Though the smaller 
species have not been identified, their size, color, and other characters were noted 
carefully enough to enable us to determine that they are also widely distributed 
along the lower edge of this belt, as well as just below it. 

Microcoleus chthonoplastes, and less frequently M. tenerrumus, may also 
enter rather sparsely into the make-up of the felts we have mentioned. The 
former species is found widely, though locally, distributed about the whole 
shore of the harbor, chiefly between the 6 and % foot levels. The gelatinous 
matrix of these alex apparently aids in giving substance to the composite felts 
or more gelatinous incrustations. But M. chthonoplastes also occurs on the 
bare mud between stalks of Salicornia or Spartina in nearly pure, irregular, 
olive-green patches, several centimeters across. In these gelatinous patches a 
sparse admixture of one or more species of Lyngbya, of Microcoleus tenerrimus, 
and of an Oscillatoria may sometimes be present, which, however, does not 
destroy the glistening, slimy appearance of these masses. 

Two species of Nostoc were noted near the upper limit of this belt, in the 
neighborhood of fresh-water streams. The smaller species, found at 1,010 
north by 1,060 east at 7 to 7.5 feet, had cells 3 to 3.54 in diameter. It formed 
brownish gelatinous lobules over the mud. ‘The second and larger species, 
found at 560 south by 890 east at 7 to 7.5 feet, had cells 5.54 and heterocysts 
6.54 in diameter. It forms a smooth, brownish coating over the mud. 

Aside from the scattered bits of Oscillatorta just mentioned, alge of this 
genus are not frequent on the mud or pebbles of the shore at this level. Several 
species occur between these levels on piles, wrecks, and on the bell of a hydraulic 
ram at 2,380 north by 1,000 west. 

Polycystis elabens is a minute bluish-green alga, the spherical cells of which 
are aggregated in a gelatinous coat over the mud, among plants of Spartina 
patens, on the Marsh at 7 feet above mean low water. It is quite probable that 
it occurs elsewhere, since it and its associates are so small as to be readily 
overlooked. : 

hivularva is represented by 2 species on the shores in this belt. R. plicata is 
found on the eastern shore near 400 north at 7.5 to 8 feet, on mud among 
clumps of Jris versicolor. The soil here is saturated with fresh water, either 
seeping or trickling from springs a few feet further up the beach. No salt could 
be detected by taste in the sap of root or leaf of plants growing in this soil. Of 


ALG OF UPPER LITTORAL BELT 95 


course, an alga growing on the surface must be immersed in salt water from 
1 to 3 hours each tide, except during a few neap tides of each series of neaps. 
But in the 9 to 11 hours in which the Rivularia is exposed, if it takes up any 
water from the soil, to which it is closely attached, it must be fresh or nearly 
fresh water. Another evidently distinct species of Rivularia was found occa- 
sionally between the 7 and 8 foot levels on sunken logs (1,240 north by 575 
west). 

Spirulina tenussima: One of the surprises of the study of the felts on the 
Spit was the discovery of occasional threads of Spirulina scattered among the 
other alge. It is evidently able to persist here when protected by the other 
constituents of the felt, and by the shade of the seed plants, though it does not 
form gelatinous coats, as it does over the Zostera near the low-water level. 

It is evident from the above description of the distribution of these Schizo- 
phycee, as well as from the account given earlier of the growth on the wharves, 
that the 6.5-foot level is not a dividing-line that marks absolutely the upper or 
the lower limit of distribution of certain of these blue-green alge. That is, 
some forms that are equally characteristic of the mid-littoral belt may be rather 
abundant just above the 6.5-foot level, e. g., Anabaena torulosa, Lyngbya 
estuaru, Sprvrulina tenuissima, and Microcoleus chthonoplastes. On the con- 
trary, other species that are characteristic of this upper littoral belt may occur 
in the next lower belt. For example, Calothrix crustacea, Lyngbya semiplena, 
etc., are usually found above the 6.5-foot level, except where unusual local 
conditions have prevented the Spartina glabra from reaching its normal upper 
limit. In such places the Calothrix pushes down the beach to the upper edge 
of the Spartina, even as low as the 6-foot level. 


CHLOROPHYCEA. 

All of the Chlorophycee of this belt, with the possible exception of a species 
of Ulothriz, are forms that are characteristic of the belt below. They manage 
to push up into the present belt, however, in certain especially favorable locali- 
ties where the shade, the character of the soil, or the running water of tide- 
streams or fresh-water rivulets render the bottom constantly wet or damp. 

The species of green alge which have thus far been noted above 6.5 feet are 
the following: 

Cladophora expansa is found somewhat frequently on the west shore of the 
harbor at 7 feet, as a minor component of the looser mats of Lyngbya, Rhizo- 
clonium, Microcoleus, etc. It reaches its higher limit of 7 to 7.3 feet near 
fresh-water inlets, where it forms thin but nearly pure tangles over the soil, 
between the plants of Scirpus robustus (1,670 north by 750 west). A very 
striking characteristic of this Cladophora, as developed at these high levels on 
the beach, is the sparse branching. This has already been referred to in speak- 
ing of this alga in the mid-littoral belt. In many plants the successive lateral 
branches may be separated by 15 or 20 cells of a perfectly simple main axis. 
In April 1911, tufts of Cladophora were abundant in the Inlet, but nothing 
could be seen of these tangles of Cladophora along the upper beach. It is 
probable that some of the filaments of green alge found in the felts above 6.5 
feet on the Spit and Marsh are really threads of Cladophora, but their short- 
ness and the entire absence of branches make it impossible to determine whether 
these are fragments of Cladophora, of Rhizoclonium, or of Chetomorpha. 

T 


96 THE RELATION OF PLANTS TO TIDE-LEVELS 


Enteromorpha clathrata is another alga which pushes up beyond the 6.5- 
foot level. Fragments of this species in good living condition are found matted 
in the looser felts of blue-greens and Rhizocloniums along the west shore, up 
as far as the 7-foot level. This alga has not been recorded growing at levels 
above 6.5 feet on the Marsh and Spit, though tangled masses of it are often 
thrown up by high tides. It seems probable that this species and the asso- 
ciated alge are able to persist at higher levels on this west shore than elsewhere, 
because of the greater dampness of the soil, due not only to the abundance of 
fresh water, but also to the shade from high trees which protect this shore from 
the drying effects of the sun during low tides occurring in the afternoon. 

Enteromorpha intestinalis is a species which is absent from the Spit, but 
which pushes up into the present belt on the other three sides of the harbor 
wherever there is a fresh-water rivulet for it to grow in. The upper limit of 
this alga is pretty constant at 7 feet, the uppermost individuals being relatively 
small plants of 6 or 8 cm. in height. It is an interesting fact that this species 
does not push up to a higher level along the shady western shore. This fact 
seems to confirm the suggestion offered above, that this species, which actually 
grows in the fresh-water rivulets, nevertheless needs contact with salt water 
for an hour or two each tide. Its ascent to high levels does not seem to be 
prevented by any inability to endure long exposure to the air at low tide. Any 
plants of this species that might locate above the 7-foot level would not be wet 
by salt water at all for several tides during each series of neap tides, since these 
minimum tides barely reach the 7-foot level. 

Ilea fulvescens, as we have seen, is a characteristic form in certain of the 
larger fresh-water streams, where its upper limit is in one or two cases as high 
as 7 feet (1,020 north by 470 west) (plate virr). It is very interesting to find 
what is evidently the same species, in active condition, matted with other species 
on the south shore of the Spit at 6.5 to 7 feet (680 east). It is hard to see what 
conditions present at this high level on the Spit can make life possible for an 
alga that is elsewhere accustomed to constant submergence, and, in fact, for 
most of each tide to submergence in fresh water. 

Monostroma latissimum is still another alga associated, as we have seen, 
with fresh-water inlets. Where these are present it often pushes up to the 
7 or 7.5 foot level, as in the Creek south of the harbor (plate vi1r) and in 
several larger rivulets along the west shore. It seems more tolerant of prolonged 
submergence in fresh water than Hnteromorpha intestinalis. 

The two species of Rhizoclonium, R. riparium and R. tortuosum, which we 
have found so generally distributed in the next lower belt, on wharves, and 
among the Spartina glabra, are also the most abundant and widespread green 
alge in the present belt. Not only are they widely distributed horizontally 
about the harbor, but they push far up the beach, often to the 7.5-foot level. 
In the shade of seed plants on the beach, or among the stones of the wharves, 
they may occasionally get up to the 8-foot level, or slightly above. In the lower 
parts of this belt the Rhizocloniums are scattered through the firm mats of . 
Lyngbya, Microcoleus, etc. At the higher levels they are found in sparse webs, 
with sometimes a slight admixture of Cladophora, clinging about the bases of 
the seed plants that shade them. The uppermost threads of Rhizoclonium seen 
were associated with a Rivularia about the bases of Iris versicolor at the 8-foot 
level (480 north by 1,070 west), or were growing among the Spartina patens at 


PLATE XVI 





B. An Attenuate Variety of Fucus vesiculosis, found on 


A. Fucus vesiculosus var. spiralis. 


Mud Flats. 





PLATE XVII 


oe 


[: 
A 
i 
\ 





Wall of Wharf, on West Side of Harbor, showing Upper Part of Zone of Fucus and 
Ascophyllum, growing on Brownstone. 





pierlagl 


7 
iv 








ALGA? OF UPPER LITTORAL BELT 97 


the same level (2,480 north by 800 west). It is worthy of note that these alge, 
which push up higher than any others, in fact to levels where they are not 
immersed in salt water for days at a time, nevertheless always avoid fresh water. 
Whenever these alge occur near fresh-water rivulets they are always found just 
above the level of the water flowing when the tide is out. 

One species of Ulothriz, probably U. implexa Kiitz. has been found in this 
belt at two points on the eastern side, near the 7-foot line, where wet much of 
the time by fresh water (1,010 north by 1,060 east). 

Vaucheria thuretu (or V. piloboloides var. compacta Collins) is of far less 
frequent occurrence here than in the belt below, but it does push up into this 
belt even as far as 7.5 feet at certain places on the Marsh (near 100 south by 
1,150 east) and along the shaded western shore. At 1,714 north on this latter 
shore there is a patch over a square meter in area at 7 to 7.5 feet. This alga, 
like several others noted above, avoids prolonged immersion in absolutely fresh 
water, though it is frequently found in the neighborhood of fresh rivulets, on 
soil kept moist by them. 

PHHOPHYCER, 

There are no brown alge that are truly characteristic of the upper littoral 
belt. Only two of these from the belt below (Ascophyllum nodosum and Fucus 
vesiculosus) ever get up above the 6.5-foot level. Of these, Ascophyllum only 
rarely even reaches to that level on the natural shores, as, e. g., at 1,440 north 
on the west shore, where it was found attached to stones on the bottom. On the 
wharves, however, as was noted in speaking of the rockweed association of the 
belt below, small plants of Ascophyllum may develop as high as the 7-foot level 
in protected places. 

Fucus vesiculosus is likewise rare above 6.5 feet, except on the wharves, 
where, on northern walls, or on the north side of piles, it may occur at the 
%-foot level or slightly higher. 'T'wo varieties of this species (var. spiralis and 
var. laterifructus) sometimes get up from their characteristic habitat in the 
belt below to the 7-foot level on the shore of the Spit. Nowhere do these rock- 
weeds occur in such numbers as to appreciably affect the character of the vegeta- 
tion of the shore in this belt. A possible reason for this is a general lack on the 
natural shores of stones and shells to which the plants might attach themselves. 
It would seem as if other favoring conditions, such as light, flooding by salt 
water, and high moisture-content of the surrounding air, must be present here 
to quite as adequate a degree as on the wharves. 


RHODOPHYCEA. 

As is indicated by our list, only two species of red alge push up into this 
upper littoral belt. These are Bostrychia rwularis and Hildenbrandia proto- 
typus, and each is found at these higher levels only where the conditions are 
somewhat exceptional. 

-_ Bostrychia has been found as high as 7 or 7.25 feet, but when found at this 
height it is in protected cracks in the stones, piles, or logs of the wharves, or 
more rarely (950 north by 970 east) on stones in the shade of seed plants, on 
pebbly shores. This protection from the sun and evaporation is evidently a 
decided advantage to a plant that is not reached by the high waters of several 
successive tides in the intervals between the fortnightly spring tides. The 


98 THE RELATION OF PLANTS TO TIDE-LEVELS 


higher individuals of this species are not, like those of the rockweed, dwarfed 
and sterile, but they bear tetraspores nearly as large as those growing lower 
down. 

Hildenbrandia prototypus, the wide vertical range of which has already been 
suggested, may push up to the %-foot level on the shaded rocks of the wharves 
and on pebbles in the fresh-water streams about the harbor. It may be recalled 
here that this species does not push up the streams above the limit mentioned, 
which is the highest level at which they would be surrounded by salt water 
during more than two-thirds of the high tides of each fortnight. 


5. THE SUPRA-LITTORAL BELT, FROM 8 TO 12 FEET. 


The borders of the Inner Harbor, between the 8 and 12 foot levels, differ 
greatly on different sides of it. On the north side there is a rather steep gravelly 
beach between the 8 and 10 foot levels, then a gentler, more irregular slope 
culminating in the flattened top of the Spit, at levels between 11 and 12 feet. 
On the east and west sides the natural portions of the shore in this belt are steep, 
or very steep, and in most places are well watered by springs or rivulets, so that 
typical seashore plants are seldom found above 9 or 9.5 feet. The steeper supra- 
littoral shores on these three sides of the harbor will be designated as the 
supra-littoral beach, or storm beach. 

The supra-littoral levels of the shore on the fourth, or south, side of the 
harbor form a continuation of the nearly flat Marsh, which we have seen reaches 
upward from the 1.5-foot level to about the 10-foot level, at the road forming 
the southern border of our area. This marshy portion of the supra-littoral 
shore has somewhat brackish soil-water and a different type of vegetation from 
that on the other sides of the harbor. It will therefore be distinguished as 
the supra-littoral marsh and will be separately considered. 


A. THE SUPRA-LITTORAL BEACH, OR STORM BEACH. 


This storm beach, which we are now to discuss, includes the usually steep, 
natural shores of the east and west sides of the harbor, for 1.5 or 2 feet above 
mean high water, and the south shore of the Spit from mean high-water level 
up to 12 feet. 

This belt evidently corresponds in part to the zone of “halophilous sper- 
mophytic herbs” of Warming (1909, p. 225). But the zone so called by this 
author includes also other types of plants (e. g., Salicornia and Sueda), which 
at Cold Spring Harbor are distinctly characteristic of a lower belt, and occur 
in the present one only as stragglers near its lower boundary. The present belt 
also corresponds approximately with the “ middle beach ” of Cowles (1899, p. 
115), but not entirely, since our belt includes much of the beach below the 
summer storm-line. It is, moreover, quite different as regards the character 
of its plant covering, in consequence, evidently, of the more protected position 
of the shores of the small harbor we are discussing. 

That this belt or zone is a natural one for the north shore of this harbor, with 
limits always close to the levels given, will be evident as we proceed. Because 
of the very general presence of trickling or seeping fresh water, and of the 
shade of overhanging bushes and trees, the natural shores of the west side and 
the southeast corner of the harbor, between 8 and 12 feet, differ decidedly in 
character from that of the north side of the harbor along the Sandspit. In fact, 


SUPRA-LITTORAL BELT 99 


in many places along the east and west sides, the shore between these levels 
shows little or no evidence of its proximity to the salt water. On the Spit, 
however, the environmental conditions within this storm beach belt, and like- 
wise the character of its plant covering, are much simpler and more constant, 
along the same level from end to end of the beach. We may therefore consider 
the plant covering here as more typical of the usual shore conditions between 
these levels, and we will discuss it first. 


1. StoRM BEACH OF THE Spit (FROM 8 TO 12 FEET). 


The character of the soil of the south shore of the Spit up to high-water 
level has already been briefly described. Above this level and on upward to the 
top of the Spit, which, from 500 east to 800 west, is on the average 11.5 feet 
above mean low water, the soil is either of fine gravel or, above 8.5 feet, chiefly 
of fine sand. There is, however, a small area of firm soil on the top of the Spit 
at 900 to 1,000 west. Here rubbish from gardens has been dumped, and a 
heavier soil has been formed, bearing a more varied vegetation. This area, 
because of its highly artificial and rapidly changing character, will be left out 
of our further discussion. We must, however, recognize its importance as the 
source from which many upland plants may have reached the less-disturbed 
portions of the Spit. Along the western end of the Spit, between 600 and 1,000 
west, and between the 8 and 8.5 foot levels, the sand has a considerable admix- 
ture of humus. A few patches of similar soil are found between these levels on 
the eastern half of the Spit near 600 east. On the top of the Spit also, where a 
denser permanent vegetation is present, e. g., near 600 west and from 0 to 200 
east, a considerable amount of more or less decayed plant remains has collected 
in the sand. Elsewhere the soil is a sand, the dry, superficial layer of which is 
readily shifted about by wind and water, though the deeper layers are held more 
firmly by the rhizomes and roots of Ammophila and, less frequently, by those of 
other plants. The slope of the beach, above the 8-foot level, varies from a rise of 
1 foot in 40 feet in certain places (e. g., 400 and 600 east, and 900 west), to a 
steepness of 1-foot rise in 8, 10, or 12 feet along the middle portion of the Spit. 

The plant covering of this belt differs from that of the lower belts we have 
discussed in its sparser character and in its less distinct zonation (plates Vv, XIII, 
and xiv). The dominant plant over most of this belt is Ammophila arenaria, 
which spreads from the 8.5 or 9 foot level on the south side, up over the top of the 
Spit at 11.5 or 12 feet and down not quite so far on the north side. All other 
species are scattered generally and sparsely over the Spit, or occur in a few local 
groups. While only 6 or 7 of the 40 species found here have a lower limit of 
distribution at all closely approaching the 8-foot level, they do range with the 
Ammophila up to the top of the Spit and down the north side. The remaining 
thirty-odd species are chiefly upland plants, not at all characteristic of sea 
beaches, and are distributed over the higher parts of the Spit in a manner 
giving no evidence of clear zonation. The most clearly distinguishable con- 
tinuous horizontal boundary along the beach, above the Spartina glabra, is the 
sparsely covered, or usually nearly bare, strip of gravelly beach between 7.5 
and 8.5 feet. This is the region where the beach is washed by the waves of 
the Inner Harbor during ordinary high tides of summer. The gravel at this 
level is more disturbed than at lower levels, the particles being moved about 
almost daily. In summer it is only when the water has risen to near the high- 


100 THE RELATION OF PLANTS TO TIDE-LEVELS 


water mark that the waves formed in the harbor can force their way through 
the belt of salt reed-grass to the gravel beach behind it. When the water is at 
a lower level this grass serves as a complete barrier to the waves. © The strip of 
gravel beach is generally most bare, therefore, where the reed-grass belt is nar- 
rowest, and has something of a sprinkling of plants where this Spartina belt is 
wider. (See plates vand xiv.) The plants occupying this gravel strip between 
7.5 and 8.5 feet are, as we have seen above, chiefly species from the next lower 
belt, such as Spartina patens, Salicornia europea, Sueda, and Atriplex, though 
there is in some places a sparse sprinkling just below 8.5 feet of characteristic 
plants from the belt above, e. g., Solidago, Cakile, Salsola, and more rarely of 
Ammophila and Agropyron. 

The naturalness of the 8-foot line as the boundary between these two belts is 
evident from such facts as those just pointed out. Of the characteristic species 
of the upper beach between 6.5 and 8 feet six have been found at, or slightly 
above, the 8-foot level. But these were in places where conditions were 
evidently more than usually favorable, and none of the plants ascended higher 
than 8.25 or 8.5 feet except Atriplex arenarta, which is recorded once from 8.75 
feet." 

The usual upper limit of distribution of the characteristic plants of the 
upper littoral beach is at the 8-foot level. On the other hand, the normal 
lower limit for the four most characteristic plants of the Storm Beach is also 
very near the 8-foot level.’ 

The reason for giving 12 feet as the upper limit of the storm beach is that 
this is the height of the highest winter storm of which we have definite record. 
It is also the elevation of the highest part of the Spit and thus of the uppermost 
soil about the harbor bearing a vegetation that shows the direct influence of the 
marine environment. 

The typical distribution of the six species of plants from the upper beach 
which wander up into the storm beach, or rather into the gravel strip separat- 
ing it from the upper littoral beach, is illustrated by the chart of the belt 
transect of the Spit drawn by Professor Conard (plate xiv). This will be 
referred to incidentally in giving the distribution of the characteristic plants 
of the storm beach. It may be noted here in passing that of these plants from 
the upper beach, only the two grasses, Spartina patens and Distichlis spicata, 
are perennial. The other four species (Atriplex arenarw, A. patula hastata, 
Salicornia europea, and Sueda maritima) are annuals, and their exact local 
distribution in the areas possessing conditions endurable for them varies con- 
siderably from year to year. 

In view of the fact that the distribution of the plants of the Spit has been 
mapped in detail (plate v), and that Professor Conard has made a special study 
of the vegetation of two limited areas (plate xiv and fig. 2), we will only note 
the more general features of the dissemination of plants growing here. 


1 These species with their wsuwal upper limits and their extreme upper limits are as 
follows: Atriplex arenaria, 8 and 8.75 feet; Distichlis, 7.5 and 8.5 feet; Limonium, 
7.5 and 8.25 feet; Salicornia europea, 7.5 to 8.25 feet; Spartina patens, 7.75 and 8.25 
feet; Suda, 7.75 to 8.5 feet. 

?The usual lower limits and the extreme lower limits for the species are as fol- 
lows: Ammophila, 8.75 to 8 feet; Cakile, 8.5 to 8 feet; Salsola, 8.5 to 8.25 feet; 
Solidago, 8.5 to 7.75 feet. (Seedlings were found in one instance at 6.5 feet.) 


PLATE XVIII 


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MON SMOYUS JURI[G JosiIeyT oJ, “suaosaupaa 
SNONnY JO JUouIdOJeAVq JO sosVIS JUdIOTIG 


asl 


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Jo solqqed uo wnijfydoosy pue snong SUIMOYS ‘TION 008 


u10}}]0q 
‘T 1veu ‘apig 4seq “V 








STORM BEACH 101 


In discussing the distribution of those plants of the storm beach on the Spit 
which are not found at all below the limits of this belt, we may deal first with 
the 8 species there found which are confined to sea-beaches or to the similar 
shores of large inland lakes. Arranged approximately according to their 
importance, beginning with the most abundant, and indicating the usual upper 
and lower limits of distribution, these species are the following: Ammophila 
arenarva, 8.5 or 9 to 11.5 feet ; Cakile edentula, 8.5 to 11.5 feet ; Solidago semper- 
virens, 8 to 11.5 feet; Huphorbia polygonifolia, 8.5 to 10 feet; Lathyrus mariti- 
mus, 10 to 11 feet; Xanthiwm echinatum, 9.5 or 10 to 11.5 feet; Salsola kali, 
8.5 or 9 to 11 feet; Aster tenutfolius, 9 to 11 feet. 

Ammophila, as has been stated, is the dominant plant over most of the 3 
acres of sandy surface of the Spit above 8 or 9 feet (plate virB). It is a peren- 
nial grass with stiff tightly-rolling, partially evergreen leaves. These are 12 or 
18 inches high and arise from a buried rhizome that runs extensively (15 to 20 
internodes) through the sand. In April 1911, the old leaves of this grass were 
green for several inches above the soil, and it was the only evergreen form seen 
on the Spit, unless we except Salicormia ambigua, some of the shoots of which 
were green for 2 or 3 inches above the sand. The stand of Ammophila is rather 
even and not dense, varying from 50 to 200 plants per square meter (plate xiv). 
The horizontal rhizomes of Ammophila run along at a depth of from 5 to 15 cm. 
below the surface, but the roots penetrate several or many decimeters deeper 
and thus reach a soil with a pretty constant supply of water, instead of having to 
endure the very dry conditions often existing at the surface of the sand on which 
they grow. The lowest surface level reached by Ammophila is 8 feet, at which 
height it is found on the south shore of the Spit, behind the wide border of 
Spartina glabra, at 600 to 700 east (plates v and x111). The soil here is of very 
fine sand. The lower limit on the less-protected north shore of the Spit is at 9, 
9.5, or 10 feet. Even here it is at a level where its rhizomes are often washed out 
by the waves during storms. 

Cakile edentula is a broad-leafed, fleshy, partially spreading annual about 
a foot in height. It is scattered over all the more sandy portions of the Storm 
Beach, between 8.5 and 11.5 feet, and is most abundant near its lower limit. It 
forms the most important constituent of a distinct green line of scattered vege- 
tation running along the north shore of the Spit just below the Ammophzla, 1. e., 
at the 8.5-foot level, e. g., between 400 east and 400 west. This line of plants is 
made up of annuals, which are evidently from seeds that are caught in the row 
of flood-trash that settles at this level during high tides. The Cakile may, in 
some seasons, occur somewhat less abundantly, between the 8.5 and 9-foot levels, 
on portions of the south side of the Spit. Thus, in the summer of 1910, a 
rather compact group of 40 plants occupied the low spot 2,515 north by 790 
to 800 west, at the 8.75-foot level. Plants of this species occurring on the 
higher levels of the Spit are usually quite scattered, but may, under favorable 
conditions, be grouped in dozens even there, as, e. g., at 2,800 north by 100 east 
between 11 and 11.5 feet. It seems evident from the distribution of Cakile here 
noted that this plant will not withstand very prolonged submergence and that 
it requires a well-drained soil. 

Solidago sempervirens, the third in abundance of the plants of the Supra- 
littoral Beach, or Storm Beach of the Spit, is scattered over it in dozens or 
scores, between the 8 and 11.5 foot levels. It is a lanceolate-leaved, partially 


102 THE RELATION OF PLANTS TO TIDE-LEVELS 


evergreen, slightly fleshy perennial, about 7 to 9 dm. in height. It does not 
occur in distinct rows or lines, but singly or in small clusters, and its distribu- 
tion is much more independent of soils and tide-levels than that of Cakile. The 
frequency of the plants may best be illustrated by referring to the map of the 
area studied by Professor Conard (plate x1v), and also by noting the fact that 
75 plants of Solidago were found between 400 and 600 west, on the south slope 
of the Spit. A similar abundance is found at 100 to 200 east, on the top of the 
Spit, and from 900 to 915 west at 9.5 to 10 feet. From 0 to 200 west this 
goldenrod is very scarce across the whole width of the Spit, except for one patch 
of 20 plants on the south slope at 9 feet (see plates v and x11). Solidago, 
when above the 8-foot level, is a deeply-rooted plant, which draws its water- 
supply from the constantly damp layer of the sand far below the surface. 

EHuphorbia polygonifolia, the fourth species of this belt, is a small, spreading, 
deep-rooted plant that is scattered quite sparsely along the nearly bare sand of 
the north shore of the Spit, chiefly between 9 and 10 feet, at and below the 
margin of the Ammophila. It occurs still more rarely along certain parts of 
the south side, at about the same levels. (See plates v and x11i.) This species 
is so small and the individuals so scattered that it plays no conspicuous part in 
the make-up of the plant covering of the Spit. 

Lathyrus maritumus is another species which is much less abundant here 
than on the more exposed beaches of the Outer Harbor and Sound. It isa 
spreading, rather fleshy-leaved, creeping perennial, with buried stems running 
widely and deeply through the soil. Only a few dozen scattered clumps are 
present on the Spit, and these are chiefly on the north side of the western half, 
near the 11-foot level. 

Aanthium echinatum, a broad-leafed annual composite, is another plant 
common on the more exposed shores of Long Island Sound, which occurs some- 
what sparingly on the Spit. It is found chiefly on the top and the north side, 
‘from 400 east to 400 west, at 10 to 11.5 feet. In a number of places in this area 
groups of from 2 to 6 plants are scattered quite frequently. Isolated plants 
are found occasionally on the south shore of the Spit, sometimes down below the 
9-foot level. (See plates v and x11.) 

Salsola kalt is a small-leafed, fleshy annual, single plants of which are found 
just above the line of trash from summer tides at the 8.5-foot level on the north 
shore of the Spit, e. g., from 400 east to 400 west. A few dozen plants altogether 
may be found at other places on the Spit, as toward the top at 11 feet or along 
the south shore near the 9-foot level. 

All of the last four species are characteristic of the sandy beaches of the outer 
harbor, where the higher waves form a wider storm-beach, but even here they 
do not form dense and continuous growths. The chief and perhaps the sole 
reason for this is the dry and unstable nature of the substratum in which the 
plants grow. It seems clear that there must be very little real competition with 
other species in the case of most individuals of these species that do finally 
succeed in getting rooted, clear of the active waves. In plants so sparsely 
scattered there is no injury by shading, and it is only in the cases of older plants 
with extensive root-systems that there can be any appreciable competition for 
water underground. ‘There can certainly be no accumulation of injurious, 
excreted waste about the roots of any species in a soil so porous and frequently 
flushed. 


STORM BEACH 103 


The one remaining species of halyphytic plane found on the storm beach is 
Aster tenuifolius, of which some dozens of plants are present between 600 and 
800 west on the south shore of the Spit, at 9 to 11 feet. This plant is a charac- 
teristic salt-marsh plant, and occurs on the Spit only in the one place men- 
tioned. The soil here is firmer and has a larger percentage of humus than any 
soil elsewhere on the Spit. In these respects, and in the somewhat greater 
moisture content, this soil resembles that of the Marsh south of the harbor, in 
which Aster tenutfolius is found more abundantly. 


UPLAND PLANTS ON THE SPIT. 

Aside from the 8 species of halophytic herbs or “ psammophytes” of the 
supra-littoral belt, whose distribution has just been described, the 33 remain- 
ing seed plants on the Spit are species which also occur on uplands entirely free 
from the influence of the sea. There are also several lichens, species of 
Cladonia, on the sand, of which only one was found in fruiting condition. 

Of these 33 upland plants, 15 are herbaceous dicotyledons, including Ambro- 
sia artemisiefolia, Anaphalis margaritacea, Chenopodium album, Euphorbia 
maculata, Galium claytom, Gnaphalium (polycephalum ?), Lactuca sp., Molluga 
verticillata, Nepeta cataria, Oenothera biennis, Oxalis stricta, Polygonella 
articulata, Portulacca oleracea, Taraxacum officinale, and Verbascum thapsus. 

There are 9 herbaceous monocotyledons, including Allium vineale, Asparagus 
officinalis, and 7 grasses and sedges (Agropyron repens, Cyperus filiculmis, 
Eragrostis minor, Panicum sp., Poa compressa, P. pratensis, Setaria viridis). 
Running over the sand, rather than climbing, are 3 lianes (Polygonum scandens, 
Psedera quinquefolia, and Rhus toxicodendron). Finally, there are 6 shrubs or 
trees, Ailanthus glandulosa, Gleditsia triacanthos, Quercus (a seedling found 
in 1909, absent in 1912), Rhus glabra, Robinia Pseudo-acacia, and one plant of 
Salia sp.? 14 feet high. For the general distribution of these see plates v, XIII, 
and XIV. 

Of these 33 seed plants, 23 are perennials, 3 are biennials, and 8 are annuals. 
_ The only evergreen species on the beach is Ammophila. 'The shoots of all other 
species do not push up till late April or early May, and they disappear again 
in mid-autumn, with the exception perhaps of Selidago sempervirens, which is 
somewhat more persistent. Thus the whole plant, root and shoot, of both peren- 
nials and annuals, is probably inactive at the time when the waves of the severe 
winter storms surround these roots and shoots with salt water. There is, in 
fact, some question whether the water ever becomes very salt about the deeply 
buried roots of many of these plants on the higher levels of the Spit, for probably 
the deeper soil-water is normally never far from fresh. (See Kearney, 1904, 
p. 424, and Oliver, 1912, p. 98.) 

The ability of these plants to invade the upper levels of the Spit, 1. ¢., above 
the 8-foot level, may thus be in considerable degree due to the coincidence of 
their period of active growth, and hence of absorption of water, with the season 
of mild weather and moderate tides. The heavy spring rains must leach out 
pretty thoroughly any salt left by the high waves of winter storms, and the 
summer rains are usually sufficient to remove any salt left by the waves of 
summer storms. Moreover, the soil is usually saturated with rain water before 
the higher waves of each summer storm are blown on the beach, and hence most 
of the salt water thrown on the rather steep beach runs off before it can really 


104 THE RELATION OF PLANTS TO TIDE-LEVELS 


penetrate into the soil. Such observations as we have made seem to show that in 
summer the salinity of the soil water above the 9-foot level, at least on the south 
side of the Spit, is not very high. These would be in accord, therefore, with the 
results obtained by Kearney (1904) on the coasts of Virginia, Massachusetts, 
and California. 

Relatively few of the upland plants are able to withstand the conditions 
encountered near the mean high-water level, 1. e., below the 9-foot contour. 
Those whose lower limit of distribution is below 9 feet are the following: 
Agropyron, 8.25 feet; Chenopodium, 8.5 feet; Galium, 8.5 feet; Panicum, 8.25 
feet, and Poa pratensis, 8.25 feet. Once we get above the 9-foot level, and thus 
clear of the influence of summer storms, the conditions become endurable for 
a much larger number of species. In fact, we find at the 9-foot level, on the 
shore, or in depressions in the top of the Spit, the only habitats on the Spit for 
certain species which apparently can not withstand either the greater salinity 
of the soil-water lower down the beach or the greater dryness higher up. This 
seems true, ¢. g., of Allium, Anaphalis, Gleditsia, and Oxalis. Other species, 
on the contrary, can endure any conditions found on the Spit except the more 
saline soil-water found below 9 feet. That is, they range upward from this 
level to the very top of the Spit, at 11 feet or higher. Such species are Ambrosia, 
Asparagus, Eragrostis, Mollugo, Polygonum, Psedera, Rhus toxicodendron, 
and Setaria. Another series of species have been found only at these higher 
levels. Thus, e. g., our records show the following plants to have their lower 
limit between 10 and 11 feet: Cyperus, Lactuca, Poa compressa, Polygonella, 
and Portulaca. Finally, another series still of the plants of this belt, which 
includes most of the woody species, have not been found growing below the 11- 
foot level. The chief of these are, Atlanthus, Nepeta, Oenothera, Quercus, Rhus 
glabra, Robima, Saliz, and Taraxacum. 

The further details of distribution of the plants of these levels on the Spit 
are shown in plate xIv, in which the individual plants of a selected transverse 
strip of the Spit are indicated by a symbol for each individual, except in the 
case of a very numerous dominant species. The significance of this chart, and 
of plate Iv, giving the zonation of vegetation on another selected part of the 
Spit, will be made entirely clear by the full explanation accompanying each 
of them. 


2. THE SUPRA-LITTORAL BEACH, OR STORM BEACH, OF THE EAST AND WEST SIDES OF THE 
HARBOR (FROM 8 TO 10 FEET). 

On the east side of the harbor there is, as noted above, no really natural shore 
north of the mill at 500 north (plate 1). There is, however, a border of rather 
gravelly soil between the 7.5 and 9 foot levels, extending from about 800 north to 
1,150 north and including the eastern half of the stone pier. The wall of the 
wharves here varies from 7.5 to 8.5 feet in height and is often of loosely laid 
stones, which allows the water to wash away the soil behind the wall, often down | 
to considerably below the top of the latter. This strip of shore has somewhat the 
character of the same levels south of the mill, except that it has fewer fresh- 
water streamlets. The vegetation of this soil includes half a dozen species 
characteristic of the upper littoral beach, already referred to (pp. 74-90, etc.). 
There are also 3 species here that are found on the storm beach of the Spit. 


STORM BEACH 105 


These are: Agropyron repens, of which occasional tufts are found among, or 
just above, the Spartina patens; Cakile, which may be represented by 2 or 3 
plants in some summers (e. g., at 1,000 north in 1911) ; finally, there is Solidago 
sempervirens, which is the only storm-beach plant that is at all abundant here. 
In 1912 there were only 4 or 5 small clumps of Solidago between 800 north and 
960 north, but from the latter point to 1,150 north there were 150 clumps 
between the 8-foot and 9-foot tide-levels. These grew chiefly on the escarpment 
marking the boundary between the gravel and the moist, grassy field that lies 
just shoreward of it. 

The very wide vertical range of Scirpus americanus is well shown on this 
shore. From the dense patches of this species already mentioned as occurring 
near the 8-foot level, at 1,000 and 1,040 north (p. 84), strips of thickly scattered 
culms push upward, along the banks of the two neighboring streamlets, to the 
10.5 or 11 foot levels. (See plate x11.) 

There are no species present above 8.25 feet level on this part of this shore, 
aside from Cakile, Scirpus, and Solidago, to suggest its proximity to the sea. 

South of the mill much of this shore, between the 8 and 10 foot levels, is 
saturated by fresh water, either running over or seeping through the soil. 
During the earlier years of our work this water came in part from the mill-race 
just above, but in 1910 the water of the race was diverted, and the amount of 
water on the upper levels of this shore has thus been somewhat lessened. The 
effect of this change on the plants of the shore will probably prove an interesting 
one to observe. ‘The two projecting points of the shore, near 200 north and 300 
north, are somewhat drier and the vegetation differs somewhat from that of the 
rest of this part of the supra-littoral beach, as we shall see. 

An examination of the plant covering of the storm-beach southward from the 
mill to 500 south shows that, aside from upland species like Rhus toxicodendron, 
Solidago sempervirens is the only denizen of the supra-littoral beach of the 
Spit that grows above the 8-foot level in this southeast corner of the harbor. 
Ammophila, Cakile, Huphorbia, Lathyrus, and Salsola have not been recorded 
here during the seven years of our study. There are, however, three other 
coastal species, absent from the Spit but found on the supra-littoral marsh, 
that occur along with Solidago between the 8-foot and 9-foot levels of this shore, 
namely, Baccharis halumifolia, Hibiscus moscheutos, and Iva oraria. 

The Solidago mentioned is found generally and rather abundantly distrib- 
uted from 500 north to 200 south. For example, there were 50 plants of it 
between 300 and 500 north in 1912, some of them being below the 8-foot level. 
I¢ is still more abundant near 200 north and near 200 south by 1,200 east and 
far less abundant in most of the intervening region, where the shore is more 
nearly saturated with fresh water, and more shaded (see plate xiII). 

Of the three marsh species on this part of the storm-beach, Baccharts is least 
frequent, being represented by one small bush near 110 south by 1,220 east at 
8.3 feet. Of Hibiscus moscheutos there is one clump near 175 north at the 
8.2-foot level and half a dozen more along the fresh-water ditch from 150 to 
400 south by 1,180 east. Jvais rather frequent. For example, one bush at 210 
north, 6 at 180 north and a clump of 50 four-year-old plants near 165 south by 
1,200 east at the 8.5-foot level. In 1912 there was a group of 30 seedlings, from 
2 to 6 dm. high, near 110 to 130 south by 1,150 east. 


106 THE RELATION OF PLANTS TO TIDE-LEVELS 


It is worthy of note that those species of the next lower belt, which on the 
Spit may wander up to 8 or 8.2 feet, seldom get above 7.5 feet on this part of 
the eastern shore. Only at one drier spot here (320 north) do we find a few 
plants of two of these (Atriplex patula and Iimomum carolimanum) growing at 
8.2 feet. Not only is this true, but Spartina glabra itself is forced down to the 
6-foot level on the wetter parts of this shore. The general effect of the abun- 
dance of fresh water in the soil is to push the upper limit of the mid-littoral and 
upper littoral associations downward to 6 inches below their usual levels, on the 
Spit, on the Marsh, and on the more exposed parts of the western shore. 

On the other hand, the abundance of fresh water in the soil of this east side 
allows certain upland and fresh marsh plants to push down to considerably 
lower levels than usual. Thus, e. g., we have noted (p. 87) that Iris versicolor 
is scattered along this shore, sometimes as low as 7.5 feet (at 10 north, 350 
north, 400 north, ete.). The soil about the roots of these plants is thus probably 
fresh, though the sturdy leaves and flower stalks are submerged in salt water 
daily, except during the smallest neap tides. In like manner Samolus flori- 
bundus pushes down to the 7.5-foot level, where its shoot is also regularly sub- 
merged in sea-water, but its roots remain embedded in a soil saturated with fresh 
water. These cases illustrate an advance of these species into areas below their 
usual lower limit, similar to that of Scirpus americanus on the west side, e. g., 
at 1,230 north, where this plant follows the fresh-water rivulets down far below 
its usual lower hmit of 6.5 or 6 feet. 

A considerable number of other swamp or fresh marsh plants, though not, 
like Jris, found below mean high-water level, do grow just above it, where their 
roots and parts of their shoots are covered by the higher tides during the growing 
season. Among such forms the following are of interest: Aspidium thelypteris 
occurs in several clumps at 8.7 to 9 feet (near 400 north). The tall shrubs 
Benzown estiwale and Clethra alnifolia are found on wet, springy banks at 8.5 
to 8.8 feet (e. g., 10 to 70 north); Cicuta maculata is found occasionally in 
saturated soil just above the 8-foot level (110 south) ; Hupatorium purpureum 
and Lysimachia terrestris also occur as low as 8 feet near the latter point; 
Sagittarva latifolia forma obtusa grows at the 9-foot level in an area where fresh 
water is present in the soil, though not abundant enough to run off from the 
surface (near 200 north); finally, Symplocarpus fetidus also pushes down 
below the 9-foot level (e. g., 110 south). 

The highest storm-tides observed during the session of the Laboratory, July 
1 to August 15, reached slightly above 10 feet. Night tides rising to 8.5 feet 
or more occur for several days in succession during spring tides. It will be 
interesting, while keeping in mind the height of these extreme summer-tides, to 
note the more important inland plants, besides the few marsh plants just men- 
tioned, that have been seen below the 10-foot level on this wet eastern shore. The 
following are the more important of these species, with the lowest level at which 
each has been found: Alnus incana, a number near 200 north at 9 feet, on soil 
rather dry at the surface; also dense clumps, 12 feet high, at 9-foot level, from 
50 to 100 south; Ambrosia artemisiefolia, near 350 north at 9 feet; Asclepias 
wncarnata near 100 south, at 8.2 feet, in very wet soil; at 350 north in better 
drained soil at 9 feet; Convolvulus sepium, 200 north, at 8.5 feet; Daucus 
carota, 350 north at 9 feet ; Hquisetum arvense, 400 north at 9 feet; Hupatorium 
perfoliatum, 110 to 120 south at 8.2 feet, and 350 north at 9 feet; Hypericum 


STORM BEACH 107 


virginicum, 350 north at 9 feet, and rather generally along this part of the 
shore: Impatiens biflora, 350 north and scattering to 110 south at 9 feet; 
Juncus canadensis, 400 north at 8.5 to 9 feet; Lycopus virginicus, 340 to 360 
north at 9 feet; Prunus serotina, 355 north at 9 feet; Psedera quinquefolia, 110 
to 150 south at 9 feet; Pyrus malus, 320 north at 8.5 feet; Rhus toxicodendron, 
110 south and 200 north at 9 feet and generally along the shore at this and 
slightly higher levels; Rhus vernix, 115 south at 9 feet; Rosa carolina, 200 to 
400 north at 8.8 and 9.2 feet, and 150 south at 9 feet; Rubus allegheniensis, 
350 north at 9 feet; Sambucus canadensis, 345 north at 8.5 feet, and a clump 
5 by 15 feet 480 north at 9.2 feet; Solidago canadensis, 350 north at 8.7 feet; 
Vernoma sp., 300 north at 8.5 feet. 


THE SUPRA-LITTORAL BEACH ON THE WEST SHORE OF THE HARBOR. 


Only a small portion of the west shore above the 8-foot level is now in really 
natural condition. Starting from 620 south by 680 east and going northward, 
we find that the upper levels have been much changed. Most of the storm- 
beach up to the corner of the tide-pond (180 south by 380 east) has been altered 
by the construction of a walk and a pump-house and by filling in along the 
lower edge of the garden of the Station for Experimental Evolution. The only 
characteristic storm-beach plants found along this part of the shore are 
Baccharis halimifolia, Iva oraria, and Solidago sempervirens. A few beach- 
plants from the belt below may now and then occur on this part of the shore 
slightly above the 8-foot level, e. g., Atriplex patula and Scirpus americanus. 

Baccharts is a robust, composite shrub 2 meters high, of which two widely 
separated plants have been found along this shore between the 8.5 and 9-foot 
levels (500 south by 650 east, 300 south by 620 east). It is interesting to note 
that this species is represented by only three other specimens about this harbor 
(2,200 north by 870 west, 160 south by 1,200 east, 240 south by 1,210 east). 
It is abundant, however, on the sandy shores of the Outer Harbor. 

Iva is an interesting half shrubby composite, sometimes a meter high, which 
is confined to the Marsh and its eastern and western borders (plates xr and 
x11). On the shore we are now considering there is a large clump of these 
plants near 310 south by 580 east at 8 to 8.3 feet, and a single plant at 500 south 
by 670 east, while on the north shore of the tide-pool (20 south by 260 to 370 
east) some 20 clumps of Iva have established themselves on gravelly soil near 
the 8-foot level. 

Solidago sempervirens is scattered in dozens along this whole shore, at and 
just above the 8-foot level, from the causeway to the tide-pond. It is most 
abundant on a rather dry, sandy point of the shore near 260 south by 590 east. 
About the tide-pool at 100 south by 300 east only two storm-beach plants are 
found. About a dozen Solidagos are scattered along the road forming the 
southern border of the pool. On the gravelly outer edge of the walled wharf 
from the tide-pool westward and northward to 540 north, at the 8 to 9 foot 
levels, 75 or 80 Solidagos are present; 50 are between 200 north and 400 north. 
In some seasons these plants are accompanied by a few of Salsola kali. 

From 540 north to the Spit, on this side the shore, above the 8-foot level, 
has been less modified than the part south of here, except for the four wharves 
near, 1,100 north, 1,500 north, 2,100 north, and 2,200 north, respectively. This 
shore is of a sandy loam, or near the entering rivulets, of black peaty muck. 


108 THE RELATION OF PLANTS TO TIDE-LEVELS 

The shore slopes rather gently downward to the 9.5 or 8.5-foot level, and then 
by a cliff-like drop of a foot falls to the often gravelly and gently sloping upper 
littoral beach. In some cases near the streams the beach above and below the 
8-foot level forms a nearly continuous slope (plate x111). The whole of this 
beach between the Spartina glabra and the dense growth of inland species is 
often only 2 or 3 yards in width and 1.5 feet in vertical range. The con- 
sequence is that it forms but a slight variety of habitats for denizens of either 
the upper littoral or the supra-littoral belt. 

The only plants of the storm beach along this shore which show any marked 
effect of the marine conditions are those growing just at the foot of the miniature 
escarpment, or on top of it, but near its edge. In other words, the real storm 
beach here has a vertical range of but 1 or 1.5 feet. 

Just back of this edge the rich soil is usually well-watered, and bears a dense 
covering of stream-bank or marsh species of inland types. Most of the shore is 
well shaded by shrubs and trees of several species to be mentioned later, and this 
shade also favors the inland rather than the marine species, since most of the 
latter are not very tolerant of shade. It is probably chiefly because of this shade 
that characteristic storm-beach plants are few in both species and individuals 
on this shore. The three species recorded are Solidago sempervirens, a few 
hundred plants; Xanthiwm echinatum, a few scattered plants on well-drained 
sandy soil (740 to 800 north) ; Iva oraria, a single plant at 2,525 north. 

Solidago sempervirens is scattered pretty generally though not evenly along 
the beach. There are often a dozen clumps in a few yards, and then for many 
yards there may be none at all or but one or two small clumps. There are 12 to 
15 plants between 640 and 700 north; 15 to 20 plants grouped near 720 north; 
25 between 740 and 800 north; 20 near 1,000 north, and about 30 clumps at 
the south end and 20 at the north end of the Research Laboratory wharf. North 
of this, up to 1,600 north, the Solidago is more scattered. Between 1,600 and 
1,700 north there are 30 plants. In the next 400 feet northward there are three 
or four groups of 5 to 20 plants each. On the wharf at 2,200 north, there are 
100 plants growing at the 10-foot level. The majority of the plants on this 
shore are found between the 8 and 8.7 foot levels, although this Solidago may 
get down to the 7.5-foot level and more rarely to 7 feet. It grows beside the 
fresh-water rivulets, but not in them, and is confined to sunny areas. It 
seems evident, from the observations made here and on the Spit, that Solidago 
sempervirens does not ascend to higher levels along the west shore because 
of the competitors encountered. The latter are more abundant and more 
varied here than along the Spit, because of the better conditions for their 
growth. The species with which Solidago is most often mingled near its upper 
limit here is Convolvulus sepwwm, though at other points it may be associated 
with Rumez obtusifolius (1,230 north), and more rarely with Atriplex, Scirpus 
americanus, or Spartina patens. Its lower limit of distribution may also be 
regarded as fixed by competition, as it can grow at lower levels, for flowering 
plants of it were found in 1912 below 6.5 feet (400 north by 1,060 east). It is 
probably enabled to reach these lower levels because the moderate amount of 
fresh water in the soil at many points, though not too much for the Solidago, is 
more than can be endured by the competing halophytes from below. 

Of the 30 other seed plants found in this belt on the west shore, all are inland 
forms except 4—Atriplex patula, Limonium carolinianum, Scirpus americanus, 


PLATE XIX 





A. Looking Northwestward over Marsh, from 1,150 East on Causeway. The 
Symbols indicating Vegetation are those given on pp. 153-156. 





B. Contact of Scirpus americanus and Spartina patens, near 400 South x 1,000 
East. Boardwalk on extreme left. Photo by P. M. Collins, 1909. 





PLATE XX 





A. Looking Northward from 900 East on Causeway, over Marsh, showing Spartina 
patens and Juncus gerardi (middle distance), Spartina glabra (at left), and 
Scirpus americanus (foreground). 





B. South Shore of Spit looking Eastward from 200 East, showing Spartina 
glabra, S. patens, Distichlis, Solidago, and Suwda. The Numbered Stakes 
mark Tide Levels on Beach. 





STORM BEACH 109 


and Spartina patens. Each of these, as we have already seen, may wander up 
from the belt below to a little above the 8-foot level. 

The frequency and the lower limit of distribution of the 26 species of inland 
plants found on the western shore between the 8 and 10 foot levels will now be 
noted briefly. ‘The level given in each case is that of the surface of the soil 
surrounding the stem. The wet or damp soil mentioned is that which is con- 
stantly saturated or nearly saturated with fresh water. We must keep in mind 
while noting levels what has been said above of summer tides that reach the 
9 and 10 foot levels. 

Acer rubrum occurs near the salt water at several places. The lowest tree 
noted (1,375 north) stood on wet soil at 8.8 feet, the leaves of its lower branches 
being submerged as the tide rose above 8.5 feet. 

Ailanthus glandulosa, a large tree at 1,330 north, at the 9-foot level. 

Alnus incana is frequent along the wetter parts, and gets down to 9 feet, as 
at 1,010 north and 1,270 north. 

Benzoin estivale occurs on damp soil at the 8.7 or 9 foot level at 1,000 north, 
1,250 north, etc. 

Bidens (probably frondosa) sometimes gets down to 8.25 feet. In 1912 
there was a group of 50 at 1,020 north, and a smaller group at 1,680 north. 

Cichorium intybus is found at 8.5 to 9 feet on dry soils, as at 1,050 to 1,100 
north. It is remarkable that this rather hardy species, which grows commonly 
near by, and can withstand submergence in salt water, has not established itself 
on the higher levels of the Spit. 

Convolvulus sepium is found at several places on moderately drained soil as 
low as 8.5 or even 8.3 feet, where it is sometimes mingled with such character- 
istic beach species as Solidago sempervirens, Atriplex patula, and even Scirpus 
americanus (near 1,700 north). 

Fraxinus americana occurs on moist but fairly well-drained soil at the 8.7 
and 9 foot level, as at 1,000 north and 1,750 north. 

Impatiens biflora is frequent beside the entering streamlets, where shaded, at 
8.5 or 9 feet, e. g., 1,005 north, 1,260 north, and 1,650 north. 

Iris versicolor is found on rather wet soil, where not too shady, at 8 and 8.2 
feet. It sometimes forms clumps a meter across, as at 810 north, 1,000 north, 
and 1,350 north. 

Juniperus virginiana, which is abundant a few yards back from this shore, 
may get down on well-drained soil to 9.2 feet, as at 1,760 north. 

Melilotus alba is found abundantly on damp soil between 8.5 and 9.5 feet on 
the wharf at 1,050 to 1,200 north. 

Panicum sp. has been noted but once on this shore, but is interesting, since it 
follows a rivulet down from 8.5 to 7.5 feet near 1,220 north. 

Periploca greca: One large vigorous vine of this climber, with several dozen 
stems from 10 to 20 mm. thick, has become established on soil at 9 to 9.5 feet 
near 1,800 north. 

Plantago lanceolata and P. major are present, but less common than on the 
east side of the Harbor. They both get down to 9 feet or slightly below. P. 
lanceolata is found at 1,900 north and P. major at 1,260 north. 

Polygonum lapathtfolium and P. sagittatum are established on very wet soils 
at 9 feet, occurring in one or two spots, as at 1,262 north. 

Prunus avium has established itself all along this shore, especially near 
1,000, 1,300, and 1,740 north. On hummocks of better drained soil it may get 
down to 9.25 or even 9 feet. 

Robinia Pseudo-acacia gets down to the same level with Prunus (at 1,750 
north). 


110 THE RELATION OF PLANTS TO TIDE-LEVELS 


Rosa carolina is scattered in wet soil near the 9-foot level, e. g., 1,270 north 
and 1,750 north. 

Rumecz obtusifolias occurs occasionally near the 9-foot level, as at 1,230 north. 

Sambucus canadensis is not infrequent near the 9-foot level, but two vigorous 
specimens 8 feet high are growing at the 8.5-foot level at 1,000 north and 1,375 
north. 

Solanum dulcamara is about as common here as on the eastern shore, and is 
always found in saturated soil, e. g., 1,030 north at 8.25 feet, and 1,260 north at 
8.25 feet, rooted in the bed of a rivulet. 

Tilia americana is growing vigorously near 1,760 north at the 9-foot level. 

Vitis labrusca is the last of these non-halophytic plants to be mentioned. 
A large Concord grape which grows on moist soil near 1,670 north, at the 8.75- 
foot level, fruits abundantly. 

The interesting feature of the occurrence of these various plants at the 
levels mentioned, on most of the west shore, as on the wet and shady parts of the 
east shore, is the fact that the soil in which they are rooted is often covered by 
salt water. It may be thus submerged for 3 or 4 hours daily even during the 
growing season. It is evident that the abundance of fresh water in the soil not 
only prevents most of the xerophytic storm-beach species from becoming estab- 
lished on these wetter shores, but this fresh water in the soil prevents the salt 
water from really penetrating it. This soil, saturated with fresh water, aided 
probably by the shade, enables the inland forms to hold the soil against the 
storm-beach species that dominate these same levels on the Spit. 

In summary, the vegetation of the east and west shores from the Spartina 
glabra belt upward to the 10-foot level is made up of a few types that withstand 
very salt water about both root and shoot, but can not endure fresh water in the 
soil, e. g., Atriplex, Spergularia, and Solidago. Other forms, such as Scirpus 
americanus, withstand fresh water in the soil and a submergence of their shoots 
in salt water for 3 or 4 hours each tide, but can not withstand shade nor the 
competition of the inland species. Finally, there are the upland and fresh 
swamp species, which will not endure salt water about their roots. These grow 
in soils saturated with fresh water, at levels where this soil and the bases at 
least of their shoots may be submerged in salt water for only brief periods (1 to 
2 hours per tide), during the growing season. 


B. THE SUPRA-LITTORAL BELT OF THE MARSH, OR BRACKISH MARSH 
(FROM 8 TO 10 FEET). 

Since detailed studies and maps have been made of the vegetation of the 
Marsh (plates x1, xx1, and xxII), we may here be content with pointing out 
the important contrasts between the plant covering of this level of the Marsh 
with that of the other shores of the harbor, especially with that of the Spit. 

A striking feature of the higher levels of the Marsh, at the south end of the 
harbor, is the absence of the most characteristic plants of these same levels on 
the Spit, with the exception of Solidago sempervirens and an occasional plant 
of Atriplex patula. Plants such as Ammophila, Cakile, Euphorbia polygom- 
folia, Lathyrus maritima, and Salsola are entirely absent from the Marsh. In 
place of these species, characteristic of the gravelly beach of the Spit, we find on 
the flat, undrained peat of the Marsh a very different set of plants. Here there 
are extensive stands of Juncus Gerardi, Spartina patens, or Distichlhs, running 
up to the 8.5 or 9 foot level, there to be mingled with, or suddenly displaced by, 


FEET 


SUPRA-LITTORAL BRACKISH MARSH 1 


Eleocharis olivacea, Scirpus americanus, or occasionally by Scirpus robustus. 
Finally, at the practically fresh southeast corner of the Marsh, 8S. americanus 
is replaced by a dense stand of Aspidium thelypteris (plates x1 and xx1). The 
sharpness of the boundary often seen between the stands of different species is 
the more striking because there is no appreciable change in the level or character 
of the soil. (See plates x1, xix, and xxi.) There are, however, marked 
differences in the depth of the peaty soil overlying the gravel subsoil, and also 
in the salinity of the soil-water, of these differently covered areas (fig. 3). 


~~ Agrostis 


S é J J 
10 P Sp ff 
PRES AF I i an SET TELE ct Sp 8ft. 
8 
Surface 
of marsh 
5 Gravel Se 
Mean low water level 
600 South 500 400 300 200 100 South 0 \OON. 


Fig. 3.—Vertical north-to-south section of the vegetation, soil, and subsoil of the 
Marsh at 1,100 east. Data by H. H. York, H. S. Conard, and P. M. Collins, 1909, 1910. 
Vertical scale 1: 80. Horizontal scale 1: 1,600. ~—~-—-—~— indicates height of vege- 
tation above soil. The symbols used are explained on pages 153 to 156. 


~ Among the dominant plants of the higher Marsh are scattered other species, 
some of which are found on the Spit, but others of which are peculiar to the 
Marsh or to it and the wetter portions of the east and west shores. Occasionally 
one of these species may become abundant or even subdominant over a consider- 
able area. Thus Solidago sempervirens is scattered thickly along the western 
bank of the tide-stream from 200 to 400 south at 1,160 east. Iva oraria, a bush 
which occurs at lower levels, also forms considerable patches in this supra-littoral 
belt, e. g., at 180 south by 1,200 east, and on the west side of the Marsh from 200 
south to 500 south. Elsewhere, as about 200 south by 100 east, it is merely 
sparsely scattered. Still other species may sometimes cover portions of this 
higher part of the Marsh, of from 1 or 2 up to 30 or 40 sq. meters in area. Thus 
the rather wet “ area 2” of plate v1 is dominated by T'riglochin marviima, which 
is more characteristic of the belt below. On areas 3 and 27, Gerardia maritima 
is the dominant species (see explanation of plate v1). Areas 25 and 26 are 
dominated by a thick growth of Aster subulatus, while a dense stand of Pluchea 
camphorata is clearly dominant on area 28. Atriplex patula hastata, though 
abundant at several points on the Marsh, is always outnumbered in any consider- 
able area by one or more other species. 
8 


112 THE RELATION OF PLANTS TO TIDE-LEVELS 


The 20 or 25 other species of plants found on the higher parts of the Marsh 
are never dominant over any appreciable area, but like many of the 15 possible 
dominants mentioned above, they may be scattered more or less frequently among 
the species dominating any area. Some of these scattered species may be con- 
fined to one or a few small portions of the Marsh, while others, like the Atriplex 
mentioned, may be rather generally, though sparsely, distributed over the Marsh 
between the 8-foot and 9-foot levels. Certain of these occasional species are, 
however, rather prominent because of their size, e. g., Myrica and Sambucus; 
or because of the brilliancy of their flowers, as is true especially of Asclepias 
incarnata and Hibiscus moscheutos. 

Further details of the distribution of these plants on the high levels of the 
Marsh must be sought in the map of Professor Conard. What has been said 
here is merely to indicate the nature of the marked difference between the plant 
covering of this wet, partly brackish, sunny marsh and that of the gravelly or 
sandy, well-drained Spit, or that of the wet, shady, western shore of our harbor. 





JOHNSON AND YOR 


PLATE XxXI 


—INE]}R 


7 


SN a0) Gy Ss SAS 





 —— 


JOHNSON AND YORK. PLATE XxXI 


Oft. SECTION I. 















































































































ee 
ac ies 
3 Si 
ple ee aire os || [Hy a ee ee b 
oe ee CL err NE 
oe SoM ee a 
SESE Ss SSACSUABRUCIVENSUOMELE SNOB cone eee 
ee SanUEALUGTUNGIIL —— 
Se sremcarect dMNBRECHEN: SA UREANG i eee eee 
ee TTT 
: SLANCTASUNERRUTUUN 
SKOSIHOTETEAIAT 

























































































Lp 











v Ur 
VR 
























































N 



























Fas ws A 2 AZ Al a7 x ne ak oe > SON <3 YX \ é ONS: 
Sores A YS SS VSM ASSIS Sods ORIN WALSALL {i doy YS 
OP) Fea PUPIPPINNG MAPA Yfppes 
i eg FPL ALISA IGS NINN Soe PR Se Wy = PY) 7 . 
en Ze a ae ae MIE: 1 SN TA PP tat wa ZEN, \S38 < Le a « ee RN 


Scale 
10) 10 20 30 40 50 Feet 


: Beitr TRANsEcT oF AESTUARIAL Marsu 1050 to 1100 Bast os 
VA Spartina pateris KN \ { Juncus Gerardu il Asptdium thelypterts aes Scurpus americanus 





‘ tree 23 Spartina glabra (except near 5008) 


PLATE XXII 


JOHNSON AND 





NU 


PLATE Xxil 


JOHNSON AND YORK. 


oO 
aN 
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NBN 
2 NS a 
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Pies > a 3 
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Se n nA? Hn WD 
nn NS 
nm 


No 
WY. 


SECTION IV. 





2 a 
\ 
Se 
WS 
NOS 
X 
f a 
” Sor 
es \ 
a S 
EX 
\ 


Bett TRANSECT OF AESTUARIAL Marsu 1050 to 1100 Easr. 


50 Feet 


40 


20 


6. DESCRIPTION AND MAP (PLATES XXI AND XXII) OF BELT 
TRANSECT OF THE MARSH (FROM 1.5 TO 10 FEET), 
SHOWING THE DISTRIBUTION OF THE VEGE- 
TATION EXISTING IN 1909-1910. 


By Henry S. CONARD, AIDED BY PAUL M. CoLLINS AND CHARLES W. PALMER. 


We will give at the start a brief explanation of the construction of the map, 
plates xxr and xx11. Then, after noting the topography of the area studied, 
will take up the zonation of its vegetation in detail. 


1, EXPLANATION OF PLATES XXI AND XXII. 


This map represents a minute study of a portion of the Marsh at the head of 
the Inner Harbor, by means of a belt transect (Clements, 1905, pp. 178-179). 
The belt is 50 feet wide and extends from the wagon-road on the south to the 
open water of the harbor on the north. It lies on the general map between 1,050 
east and 1,100 east, and 525 south and 100 north. This belt was chosen because 
it represents the greatest diversity of vegetation, together with the most distinct 
zonation. Stakes were set every 50 feet along each side. Then with tape-lines 
and graduated rods the exact boundaries of the vegetative areas were plotted in 
strips 5 feet wide. Every plant was located when isolated or not forming a 
prominent part of a society. For example, every individual plant is given for 
the following species: Asclepias incarnata, Atriplex arenaria, Hibiscus mos- 
cheutos, Hypericum perforatum, Iva oraria, Myrica gale, Oenothera biennis, 
Prunus serotina, Rubus alleghemensis, Rumex crispus, Sambucus canadensis, 
Vaccinium pennsylvanicum. 

Several other species are located where they occur sparsely, or on the margins 
of their areas, but are put in diagrammatically where plentiful. This serves 
to show the limits of distribution and the areas of dominance. Such species are: 
Aspidium thelypterts, Atriplex patula hastata, Distichlis spicata, Juncus 
gerardi, Salicornia europea, Scirpus americanus, Solidago sempervirens, Spar- 
tina glabra alterniflora, S. patens, Sueda maritima. 

Carex tenera, Eleocharis olivacea, and Limonium carolinianum are marked 
where sparse, but are not designated on the map where more plentiful. They 
are mentioned in the description of the various belts. 

In every case the mark on the map is much larger in proportion than is the 
plant itself. This is a mechanical necessity. Hence also many small gregarious 
species must be diagrammatically shown. Gregarious species which do not 
become dominant are: Aster nove-belqu, A. subulatus, Atriplex patula hastata 
(in favorable places), Distichlis spicata, Gerardia marituma, Impatiens biflora, 
Juncus gerard: (when outlying), Lileopsis lineata, Lysvmachia terrestris (in 
favorable places), Plantago decipiens, Polygonum maritimum, Salicornia 
europea (in places), Scirpus nanus, Spergularia marina, Triglochin maritima. 

Diagrammatic representation was alone possible for many plants which occur 
scattered more or less profusely throughout a community. Such are: Aster 


113 


114 THE RELATION OF PLANTS TO TIDE-LEVELS 


nove-belgii, Carex tenera, Eleocharis olivacea, Hrechtites hieracifolius, Hypert- 
cum virginicum, H. canadense, H. mutilum, Impatiens biflora, Limonium 
carolinianum (in places), Lysimachia terrestris, Spartina patens (in belts of 
Juncus, Scirpus, or Spartina glabra). 

Some of the above list are not marked on the map at all. Where a series of 
parallel lines represents a species (¢. g., Spartina patens), the lines are drawn 
farther apart where the plant is less plentiful. For symbols not explained on 
plate xxi see Table F, page 153. 


2. DESCRIPTION OF THE STRIP. 
A. THE LIE OF THE LAND. 


The wagon-road on the south of the strip is macadamized, and occupies a 
causeway built about 6 feet above the level of the Marsh. The bank slopes down 
to the Marsh as steeply as the earth and gravel of which it is made would lie, 
that is, about 30°. The foot of the bank is about 9 feet above mean low water. 
Very high winter tides wash much débris as far as this bank. Thus beds of 
dead stems of Spartina glabra and occasional timbers 6 inches in diameter may 
be found anywhere over our area. 

From the foot of the bank to the %-foot contour the Marsh forms a smooth 
plain. The only irregularities are the occasional tide-pools and mud-flats 
marked on the map. The pools are flat-bottomed depressions of 4 to 6 inches 
depth. The margins are usually vertical, but sometimes the bottom of a narrow 
arm of such a pool rises gently to the level of the surrounding sod, forming a 
mud-flat. Other mud-flats of this region are not connected with any depression. 
At about the 7-foot contour, in our area, the ground falls off rapidly, or even 
abruptly. This contour marks the beginning of the dominant and pure growths 
of Spartina glabra. 


B. THE PLANT COVERING IN DETAIL. 


The vegetation of this strip shows several well-marked zones, or belts, which 
may be designated along the east side of the strip as follows: 


i. Wmoadside-graga «Belt: 2.5 eecce Oe ee 516 south to 497 south. 
Dy *ECOTT “BGIL, vote ok ee a ihe a aie oie eee 497 south to 450 south. 
33 RCW DUS OMeTICUNUS Hell... 2.07. seen 450 south to 340 south. 
4. :Jduncas-Snarting’ Belt. 500.23 ore eee 340 south to 93 south. 
5. Spartina patens Belt. aia. aele ae 93 south to 18 north. 
Se Distichiis ( Belt’, e754 a aineereee cae: 18 north to 28 north. 
7. Spartina glabra Muhl. var. alternifiora 

(Lidisel)  Merr. te. cars, Agee ees eee ee 28 north to 70 north. 


1. THE ROADSIDE GRASS BELT OR BELT OF AGRICULTURAL GRASSES. 


This area presents a uniform appearance as of a rather sterile and neglected 
grassy meadow (fig. 1). The grasses are denser and taller on the 2 feet of level 
ground at the edge of the roadbed. This area is at once seeded and fertilized by 
washings of manure from the road. The dominant species is Agrostis alba, 
which grows about 20 inches tall. With it occur: 

pS tay ae } subdominant. 


Dactylis glomerata 
Agropyron repens sparse. 
Panicum sp. 


« All measurements of height of vegetation were made after July 15, 1910. 


BELT TRANSECT OF THE MARSH Tas 


Agropyron attains a height of 30 inches. Dotted here and there occur: 


Acalypha virginica. Hypericum perforatum. Rhus toxicodendron. 
Ambrosia artemisiifolia. Juncus tenuis. Rubus allegheniensis. 
Aster sp.? Lactuca sp. Rumex acetosella. 
Barbarea vulgaris. Melilotus atba. crispus. 
Carex, 2 spp. Oenothera biennis. Solidago canadensis. 
Cerastium vulgatum. Oxalis stricta. Taraxacum officinale. 
Chrysanthemum tleucanthe- Plantago lanceolata. Trifolium agrarium. 
mum. Potentilla argentea. pratense, 
Daucus carota. Prunus serotina (2 plants). Vaccinium pennsylwani- 
Dianthus armeria. Pyrus malus (1 small cum. 
Erigeron canadense. plant). Various mosses. 


So far as these species are indicated on the map, every individual is noted. 
At the foot of the bank where moisture is plentiful we find also: 


Asclepias incarnata (3.3 feet tall). Lysimachia terrestris. 
Hupatorium perfoliatum. Myrica gale (3.8 feet tall). 
Hibiscus moscheutos (3.4 feet tall). Polygonum sagittatum. 
Impatiens bijfiora. Scirpus americanus. 


Lycopus americanus. 


The most peculiar feature of this belt, perhaps, is the group of Scirpus 
americanus which is found 3 feet up the bank, among the grasses. This, 
together with Hibiscus and Myrica, owes its presence to the nearness of the 
salt sea-water. The other plants are such as might be expected on any roadside 
bank in the Piedmont region of the northeastern United States. The total 
number of species in Belt I is 45. 


2..THE FERN BELT. 


Associated with a seepage of fresh water which comes in at the southeast 
corner of the Marsh, there is a large bed of Aspidiwm thelypterts of dense and 
luxuriant growth. Overtopping the fern is a sparse but (in our area) universal 
fringe of Scirpus americanus. The ferns are about 2 feet tall, and easily domi- 
nate their area (plates XIX A and x1xB). Their border is very sharply defined. 
They stop off suddenly both south and north without diminution in size or fre- 
quency. Outside of this belt only 4 plants of this species occur, namely, at 398 
south by 1,072 east, 403 south by 1,081 east, 448 south by 1,098 east, 449 
south by 1,089 east. This is doubtless due to the fact that the fern usually 
spreads by rhizomes, and only rarely by spores. The fern area does not extend 
quite across the belt. At the middle of the belt there is a narrow strip of marsh 
between the foot of the road-bank and the ferns. This strip is occupied by a 
dense and luxuriant growth of Lysimachia terrestris, Aster nove-belgu, and 
Impatiens biflora, the first being dominant and the last least numerous. With 
these, Myrica gale and Hupatorium perfoliatum occur as noted on the map. At 
492 south and about 1,095 east are two telegraph poles. Between them is a 
strong bush of Sambucus canadensis. 'This doubtless sprang from a seed dropped 
by a bird which perched on one of the poles. Seeds dropped in this way are 
frequent on the marsh. One bird excrement was found containing 11 cherry 
seeds (probably Prunus serotina). Other plants found among the ferns are: 


116 THE RELATION OF PLANTS TO TIDE-LEVELS 


Scirpus americanus (subdominant, Aster nove-belgii f t 
averaging 3.2 feet tall, with an occa- Impatiens biflora } kage 
sional maximum of 5.3 feet). Panicum sp. (scattered 

Agropyron repens (beside the tele- RHoeron Dis as 

picket: poles). Galium claytoni 

pias incarnata June d i 
Eupatorium perfoliatum -as charted. PO ice cna etie 


Myrica gale Selaginell (gumantss 

; : nine elaginelia apus plants). 

Erechtites hieracifolius. A liverwort (Pallavicinia). 
abundant. 


near southeast 
corner only. 


Hypericum canadense 
mutilum 
virginicum 

Atriplex patula hastata occurs frequently, but the plants are slender and 
etiolated, with narrow, erect leaves. They are hopelessly overshadowed by other 

plants. Total number of spermatophytic species 19; of pteridophytes 2. 


3. THE SCIRPUS AMERICANUS BELT. 


Scirpus americanus occurs from the foot of the road-bank to about 345 
south, being plentiful throughout this area, and of an average height of about 
1 meter. Its inner margin is determined by the road-bank. The outer margin, 
however, is hardly less distinct. For though the plants become fewer and 
shorter (2.5 feet), they greatly overtop their companion species. The outlying 
individuals were easily plotted (plate x1x B). This plant has already been noted 
as subdominant in the fern area. In the middle of its range it is clearly 
dominant. Toward its outer borders it is dominant only in appearance. In 
number of individuals it is greatly exceeded by Spartina patens. This grass, 
beginning at the margin of the ferns in some places, becomes more plentiful 
by imperceptible gradations, until it becomes dominant, and finally pure (345 
south, Belt IV). In the south and east half of Belt III, Lysimachia terrestris 
and Hypericum virginicum are frequent at the southeast, becoming sparse 
toward north and west. Hrechtites hieractfolius is abundant (about every 4 or 
5 feet in August 1909) over the southern two-thirds of the belt. The limits 
of these plants are shown on the map. Impatiens biflora has two outlying 
representatives at 450 by 1,075 and 445 by 1,050. Single plants occur of 
Asclepias incarnata, Aspidium thelypterts (as already noted), Carex lurida, 
Epilobium coloratum, Hibiscus moscheutos, Hypericum canadense, H. mutilum, 
Myrica gale. Trifolium agrarium and Rumezx crispus occur at the foot of the 
road-bank on the south. 

Carex tenera and Eleocharts olwacea are frequent in the north and northwest 
portions, the latter species extending as far south as 450 feet and 1,077 east. 
Eleocharis becomes subdominant about 350 south to 360 south and 1,050 east 
to 1,062 east. Another bed of it occurs at 400 south and 1,075 east. Carex 
tenera is abundant about 350 south to 355 south, where Scirpus is becoming 
decidedly sparse. It grows about 2 feet tall. Panicum is sparse throughout 
this zone. Lycopus americanus is represented by 2 or 3 plants near 400 south. 
Oscillatoria was noted on the moist ground at 340 south. 


* One square foot near the middle of our third belt was occupied (August 4, 1911) 
by 48 Scirpus americanus, 31 Carex tenera, 6 Aster, 1 Erechtites, 234 Hleocharis 
olivacea, 128 Spartina patens. One square foot in the densest patch of Scirpus ameri- 
canus contained 88 stalks of that species, and 32 Spartina patens, 1 Carex, 2 unidenti 
fied grasses, 1 Acer rubrum (first year seedling). 


BELT TRANSECT OF THE MARSH 117 


A boardwalk runs obliquely across the northern border of the Scirpus belt. 
It is built partly on a low ridge of gravel, hauled in for the purpose, and partly 
on posts. The gravel forms a strip about 4 inches above the level of the Marsh, 
and about 5 feet wide. The boards occupy a width of about 2 feet, and the 
plants for 2 feet on either side of them are kept mowed off with a scythe to a 
height of about 3 inches. These conditions have greatly affected the adjacent 
vegetation. Asclepias incarnata is especially abundant on the south side of the 
barrier. Juncus gerard is scattered about in the Scirpus belt north of the walk. 
Between the boards and on the gravel occur: 


Agropyron resens. Distichlis spicata. Rhus toxicodendron. 
Ambrosia artemisiifolia. Erechtites hieracifolius. Rumesx acetosella. 
Anaphalis margaritacea. Fragaria virginiana. crispus seedlings. 
Asclepias incarnata. Lactuca sp. Scirpus americanus. 
Aspidium thelypteris. Lycopus virginicus. Solidago sempervirens. 
Aster nove-belgii. Myrica gale. Spartina patens. 
Atriplex patula hastata. Plantago lanceolata. -  Paraxacum officinale. 
Bidens frondosa. major. Verbascum thapsus. 
Carex tenera. Prunus serotina. 

Dactylis glomerata. Rubus allegheniensis. 


Total number of spermatophytes aside from boardwalk area, 20; pterido- 
phytes, 1; additional species along boardwalk, 21; total, 42, 


4, JUNCUS-SPARTINA BELT, 


The fourth belt is in every way much broken and diversified. It extends from 
the limits of Scirpus americanus to the pure growth of Spartina patens at 95 
to 150 south. The 8-foot contour cuts its northern border. Many small tide- 
pools and naked mud-flats break the continuity of the spermatophytic vegeta- 
tion. With these exceptions, nearly all of the area is covered with Spartina 
patens. In places this is pure, but other large areas are distinctly dominated 
by Juncus Gerardi. So dense is the Juncus as to give the impression of a pure 
growth.* Its brown fruits, over-topping Spartina patens by 1.5 to 2 dm., give it 
a characteristic appearance which is noticeable a hundred yards away. But 
except in some few patches, Spartina is always mingled with Juncus. On the 
southern border of our belt, Juncus is scattered through the Scirpus zone as far 
as the boardwalk. Juncus also occurs scattered in the Spartina areas in several 
places. But the boundaries of the Juncus patches are usually very sharp and 
easily recorded. At 150 south and 1,100 east is a mixture of Juncus and 
Spartina which it seemed best to describe as Juncus with a mingling of Spar- 
tina (see plate xx11). There is a distinct tendency for the tide-pools to be 
bordered by Spartina rather than by Juncus. But in several cases one plant 
borders one side and the other borders the opposite side of the same pool. The 
average height of Juncus is 4.5 to 5 dm.; of Spartina 2 to 3.5 dm. or rarely 4.5 
dm. In three places (150 south and 1,050 east, 200 to 250 south, 295 to 300 


2 On 5 different plots of 4 square inches each there were counted (August 1911): 


SUNCUS QETATAT . dane. tbs cn ee i's 30 12 5 20 
Sporting patens. 05 «sie as sees 3 0 0 1 2 
Aster. eu bulatis.. ives + 2eees2 0 0 0 0 1 


This gives an average of 604.8 Juncus per square foot. In pure growths, Spartina 
patens averages about 1,400 stalks per square foot. Actual counts gave on 4 square 
inches, 40 and 43 stalks, and on 16 square inches, 151 stalks. 


118 THE RELATION OF PLANTS TO TIDE-LEVELS 


south, and 1,100 east) Spartina glabra occurs scattered among the Juncus. It 
seems to have extended, probably by rhizomes, from denser areas outside the 
belt. In all such cases it looks starved, and is not over 3 dm. tall. Between 
200 and 250 south, Spartina patens patches also contain Spartina glabra. There 
is no evidence of antagonism between the two. 

In smaller numbers and more restricted areas several interesting maritime 
plants occur in this belt. Gerardia maritima forms distinct beds. Where it 
occurs, the grass or rush is of very short stature, not over a decimeter, or may 
be wholly absent. Mud, often containing small pebbles, is visible between the 
plants. As the grass or rush gradually becomes taller around the Gerardia 
patch, the Gerardias become less numerous, taller (up to 2 dm.), and later in 
flowering. This is evidently due to shading of Gerardia by the competitor, 
reduction of light inducing taller growth, and reduction of temperature causing 
later germination and slower maturation. 

At 150 to 160 south, Gerardia is accompanied by the much rarer T'riglochin 
marituma. ‘This plant occurs only in the midst of the spots where competition 
is least. It never, in this belt transect, exceeds 1.5 dm. in height. The indi- 
viduals are numerous — a hundred or more in each patch. They seem healthy, 
and flower and fruit freely. At one place about a dozen plants of Plantago 
decipiens are mingled with Gerardia and Triglochin (160 south and 1,090 east). 
These were observed in two successive years. They seem healthy, but are of 
only medium size, about a decimeter tall. In other parts of the Marsh this 
species attains a height of 1.5 dm. with many leaves and inflorescences to each 
plant, and T'riglochin reaches a height of 2 or 2.5 dm. 

Spergularia marina was first met at 298 south and 1,075 east—an isolated 
plant. It is established on the mud-flats about 100 south, in this zone, and on 
the margins of the next. There were in 1909 about a dozen individuals, 0.6 to 
-0.8 dm. tall, flowering and fruiting freely. This species and Plantago decipiens 
occur in greater luxuriance outside our belt transect on the inner margins of the 
Spartina glabra zone, where the mud is very sparsely settled by other plants. 
Spergularia was observed in our strip in these places and only in these, both in 
1909 and 1910. 

Scirpus nanus, miniature but full grown, forms a bed at 122 south and 1,089 
east. It is in the edge of a mud-flat, along with Distichlhs, Salicornia europea, 
and Atriplex patula hastata. This is much more exposed to sun and wind than 
the place it occupies in the inner border of the seventh belt. 

The scattering plants named above are all essentially gregarious, and not 
found everywhere. The following are very common members of the vegetation 
of protected shores, but occur often as isolated individuals: 

Salicorma europea makes its first appearance in the edge of the first large 
tide-pool (315 south by 1,075 east). In the area from 250 to 300 south many 
Salicornias were dead in 1909, apparently eaten by grasshoppers. Other 
individuals gave evidence of “ damping-off” at the base. The first healthy 
plants were 282 south and 1,085 east. Between 150 and 100 south many 
Salicornias were large and bushy—excellent specimens of the species. But 
others were dying at the tips, and some were quite dead. Even the best condi- 
tions south of 100 feet are evidently unfavorable to this species. 


BELT TRANSECT OF THE MARSH 119 


Atriplex patula hastata was found in a starved condition in the shade of the 
ferns of the second belt. In the fourth belt it occurs with Salicornia in the 
edge of tide-pools and on mud-flats. The leaves spread out in the normal posi- 
tion and are of normal shape. At 250 to 275 south they were badly eaten by 
insects in 1909. The first healthy, bushy individuals in our strip, plants 3 dm. 
high and 2 to 3 dm. across, were in the edges of mud-flats between 100 and 150 
south. But just east of our strip fine specimens occur at about 225 south. 

Inmonium carolinanum was first observed at 300 south and 1,070 east and 
again at 259 south by 1,068 east. These were small, feeble plants, not flowering. 
A group of stronger plants occurs at 215 south by 1,075 east. From this point 
northward the species becomes more frequent and more vigorous. In other 
places around the harbor it is quite able to hold its own in dense growths of 
Spartina patens and Distichls spicata. It is not hurt by such competition. 

Polygonum maritimum seedlings also occur around tide-pools and mud- 
flats, sometimes in great numbers. Only at 300 south by 1,075 east were they 
found flowering, and then as slender and weak plants, not over a decimeter tall. 
In other places on the Marsh a single plant of this species may be 1.5 or 2 dm. 
tall and as large in diameter. 

Distichlis spicata, though occurring along the boardwalk, may be said 
properly to begin with the tide-pools. It never looks starved, but occurs only 
in isolated stalks or small groups from 325 to 100 south. In the tide-pools at 
100 south and 1,075 east and 110 south by 1,080 east it first shows itself as a 
real invader, spreading by vigorous straight rhizomes. It is nowhere dominant 
in this zone. 

Eleocharis olivacea does not come farther north than 313 south. Carex tenera 
was not noted outside the Scirpus belt, though it was frequent there. 

A single seedling of Iva oraria was recorded at 300 south and 1,075 east. It 
was not found in 1911. 

One small plant of Atriplex arenaria was observed on the edge of a mud-flat 
at 250 south and 1,079 east. 

Seedlings of Aster subulatus occur around the mud-flats and beds of Gerardia. 

Sueda maritima was noted along with Polygonum maritimum at 300 south 
by 1,075 east. This is our only record of this species in this belt. 

In a tide-pool in this belt were found seeds of Prunus and Rubus in bird 
droppings, and a walnut, a pine cone, and a fruit of Gleditsia, doubtless carried 
by water. 

In a pool at 320 south various Cyanophycee were noted. A bare spot shaded 
by grass at 315 south was covered with Vaucheria. In a pool at 200 south, and 
again at 125 south, Beggiatoa was found. Rhizocloniwm was seen partly covered 
with silt at 225 south, and abundant on the ground among Spartina patens at 
115 south. 

The total number of species in this belt (20) is still considerable, but less 
than in any of the preceding belts. All of the phanerogams are such as inhabit 
only saline or brackish soils. 


5. SPARTINA PATENS BELT. 


A nearly pure growth of Spartina patens extends from 100 south to 10+ 
north, being from the 8-foot contour nearly or quite to the 7-foot. This might 
be regarded as a large patch from the preceding zone. But its location and 


120 THE RELATION OF PLANTS TO TIDE-LEVELS 


appearance in the whole Marsh mark it off as a distinct area. The grass is very 
dense and luxuriant, falling over late in the season into irregular hollows and 
ridges like “ licks ” on the hair of a cow. Its even, light-green color is especially 
pleasing to the eye. At 40 north and 1,050 east it reaches a height of 7 dm., 
6 dm. at 25 north, and 5.2 dm. at 0 north. Outliers of Juncus gerard: extend 
only as far north as 81 south. Here the Spartina is only 3 to 4.5 dm. tall, and 
at 25 south it drops to 2 or 3dm. Aériplex patula hastata, Limonium carolin- 
anum, Solidago sempervirens, and Distichlis spicata are scattered about irregu- 
larly. Spartina glabra is scattered plentifully in one place, 0 north by 1,050 
to 1,075 east. The southern border of the belt is exactly like the borders of 
patches in the preceding belt. At 110 south a large bed of Gerardia occurs, 
overlapping the border. On the east side the Spartina glabra belt projects 
into this. The north and west margins of the indentation are formed by the 
precipitous banks of a tide-creek, and the change of vegetation is correspond- 
ingly abrupt. The south margin isa sloping mud-flat. Here Distichlis spicata 
is established, and is vigorously invading. An isolated patch of Distichlis east 
of this may be a relic of an old mud-flat captured by the invading species and 
then cut off by a later advance of Spartina patens across the narrow isthmus. 
Will Spartina finally possess the patch and Distichhis withdraw? Atriplex 
patula hastata, Salicorma europea, and Spergularia marina occur in full 
development around this lobe of Spartina glabra. 'Total numbers of spermato- 
phytes, 10. 

In this belt Beggiatoa, both white and pink species, were noted in a pool at 40 
south, on the contour of 6 feet 6 inches, together with Anabena and mats of 
Rhizoclomum. 

About the zero-line the grasses grow shorter and other plants are more 
numerous among the Spartina patens. Distichlis spicata in particular appears 
in rapidly increasing numbers and Spartina patens disappears by equal steps, 
giving way to the Distichlis belt. 


6. THE DISTICHLIS BELT. 


For a short space Distichlis spicata is clearly dominant, but it is not sharply 
demarcated from the preceding belt. On the north, however, it stops with an 
abrupt but very irregular border at the edge of the tall Spartina glabra. The 
margin is fringed by runners of Distichlis advancing northward in the mud, and 
Spartina glabra has numerous outliers of one-half to one-fourth normal height 
in the borders of Distichlis. The narrow strip of soft brown mud (1 to 5 or 6 
feet wide) which is not closely occupied by either grass is copiously overgrown 
with Salicorma europea, together with numerous Sueda maritima, Atriplex 
patula hastata, and an occasional Atriplex arenaria. Scirpus nanus forms dense 
mats beneath everything else at several places on the border; at the east edge of 
the belt this species is quite exposed, forming the sole vegetation over 1 or 2 
square feet. Total number of Spermatophyta, 8. 

At 25 feet north Vaucheria thuretu forms dense tufts on the contour of 6 feet 
4 inches, and Rhizoclonium was found on a block of wood at the level of 6 feet 
6 inches at 25 north. 


BELT TRANSECT OF THE MARSH Tog. 


7. SPARTINA GLABRA BELT. 


At 25 to 50 feet north, a tall growth (1 meter high) of Spartina glabra 
becomes the dominant vegetation. Nothing else is apparent. Its inner border 
has been described above; its outer border is the open water. The ground 
consists of a soft, brown, oozy mud, whose surface slopes decidedly toward the 
north. It is cut by many tide-channels from 3 to 18 inches deep. 

On close examination we find isolated shoots of Spartina patens as far as 10 
or 15 feet north of the boundary of this zone. They are represented diagram- 
matically on the map, actually occurring much closer together than marked. 
Within 2 or 3 feet of the south margin, Distichlis spicata and Salicornia 
europea are plentiful. Scirpus nanus makes a dense growth on the west, just 
within the border of this zone. The most notable secondary species, however, 
is the tiny umbellifer Lileopsis lineata. Not over 0.4 dm. in height, it forms a 
dense sod on the west side of our belt, growing luxuriantly and flowering and 
fruiting freely. The shade of Spartina glabra and two daily baths with salt 
water seem to furnish the necessary conditions for its existence. It occurs 
here only, on our strip. Beyond this the seventh belt is a pure growth of 
Spartina glabra. It reaches a height of 9 dm. at 50 north and 13 dm. at 70 
north. No other spermatophyte apparently can meet the conditions here. Total 
number of spermatophytes, 6. 

As this belt is the most constantly wet with salt water, it supports the smallest 
number of species. Are they the most specialized ? 


a Fifty stalks per square foot (33 on one, 68 on another sample foot). 


IV. FACTORS INFLUENCING THE DISTRIBUTION OF 
LITTORAL PLANTS. 


The factors which most directly condition the distribution of littoral plants 
in this harbor are: the character of the substratum, water-currents, tidal changes 
in level, salinity of the water, and (probably) the temperature of the water. 
We will consider these in the order mentioned. 


1. SUBSTRATA. 


The substrata supporting plants of the shore and harbor bottom may be: 
(A) living plants or animals; (B) non-living substrata. 


A. LIVING SUBSTRATA (PLANTS OR ANIMALS). 


The only animal of great importance in serving as an attaching place for 
plants is the abundant black mussel, Mytilus edulis. This has become increas- 
ingly abundant in recent years and now nearly covers the bottom over some 
acres, in the region between 1,600 and 2,000 north by 200 to 1,000 east, and the 
region between 1,200 and 1,800 north by 200 and 400 west. As we stated in 
Chapter III, the young mussels become attached to the large sheets of Ulva by 
thousands, so as to make the bottom covered by the Ulva and its burden look 
black. The erectly standing mussels serve to catch the silt and organic débris 
that is drifting along near the bottom and thus the mussels become partially 
buried. As the shells of the mussels become larger, firmer, and rougher, the 
spores of Ulva and Hnteromorpha clathrata, settling upon them, give rise to 
numberless young sheets or threads of these alge, which wave back and forth 
above the upturned edges of the shells of this mollusk. It thus, in turn, becomes 
a substratum for more plants of the species on which the mussel itself first 
settled. The Ulva and EHnteromorpha then serve to still further retard the 
movement of the water near the bottom and thus increase the rate of silting up, 
until large areas may thus become covered with fine black mud to a depth of 
2 feet or more. 

Other animal substrata supporting plants are the oyster Ostrea virginica, 
and the various gasteropod shells inhabited by hermit crabs. The oysters of the 
Inlet, for example, often bear plants of A gardhiella, Polysiphonia, or Ceramium 
in addition to the green alge found on the mussels. 

The plants that are most important in serving as substrata for other plants 
are Spartina glabra, Zostera, and Ulva. 

Most of the species found on Spartina, like the Lyngbyas, Microcoleus, 
Rhizoclonwum, and Vaucheria, are seldom attached by definite holdfasts, but 
simply tangled about each other over the stalks of this grass in mats. Rarely a 
few small plants of Ulva or Enteromorpha are found actually attached by 
holdfasts. 

Zostera really bears a more definitely specialized epiphytic flora than any 
other plant serving as a substratum. Any of the Zostera below mean low water, 
especially that subjected to the swifter tidal currents, may bear epiphytic tufts 


122 


SUBSTRATA 123 


of the diatoms Melosira and Navicula, of Enteromorpha clathrata, and still 
more frequent tufts of the red alge Ceramiuwm rubrum and C. strictum. A 
single leaf of Zostera may often bear two or three dozen tufts of these various 
alow, and the leaves are often broken off by the weight of this load, to be finally 
stranded on the beach. The two Ceramiums are practically confined to the 
Zostera. Aside from an occasional plant, on a pebble or shell in the Inlet, these 
Floridez find no other resting-place in this mud-bottomed harbor. In addition 
to these larger forms, Zostera may bear thousands of small, sedentary diatoms, 
like Cocconeis, and sometimes many square feet of a stand of Zostera may have 
the leaves fastened together and weighted down by the gelatinous colonies of a 
Spirulina. 

Ulva serves not merely for the attachment of Cocconeis and other diatoms 
occurring singly or in very small colonies, but may occasionally bear young 
plants of Enteromorpha clathrata and may also be weighted down by the gelat- 
inous colonies of Spartina just mentioned. 

Besides the three important species above mentioned that may serve as sub- 
strata for epiphytes, many seed plants of the upper littoral belt, such as Sali- 
cornia, Sueda, and especially Spartina patens, may, like Spartina glabra, have 
felts of Rhizoclonwwm and various blue-green alge tangled about their stems. 
Finally, any alga in the harbor, if of considerable size, may bear epiphytic 
diatoms of various species. 


B. NON-LIVING SUBSTRATA. 


By far the larger number of species found in the Inner Harbor, aside perhaps 
from the diatoms, grow on a non-living substratum of either purely inorganic or 
partly organic origin. These non-living substrata may be grouped as follows: 
(1) soils, including gravel, sand, mud, humus, and peat, among the constituent 
particles of which the holdfasts, 7. ¢., roots and rhizomes, of the seed plants are 
embedded; (2) solid substrata, including rock, stones, pebbles, shells, and 
wood. ‘To the surfaces of these the holdfasts of the various alge are attached 
without penetrating appreciably into their substance. Of course, it is evident 
that felt-forming alge like Lyngbya, Rhizoclonwum, etc., may grow on the 
surface of peat, sand, or gravel. But to these alge, since they do not penetrate 
these substrata, the latter are the equivalent of solid substrata. The pebble of 
the south shore of the Spit is to a Calothrix what a stone of the wharf is to a 
Fucus or Ascophyllum. 


1. Sorts AS SUBSTRATA (GRAVEL, SAND, Mup, HUMUS, OR PEAT). 


The soils about the harbor differ in fineness from fine silt or mud up to sand, 
or even pretty coarse gravel. They differ largely also in the proportion of 
organic content from nearly pure sand or gravel to humus and peat with a very 
large proportion of material of organic origin. 

_ There is a very distinct horizontal zonation evident in the general distribution 
of soils about the natural shores of the Inner Harbor from the bottom up to the 
10 or 12-foot level. As has been mentioned in speaking of the distribution of 
Zostera, the portions of the bottom lying below 1 foot are chiefly of a sandy, 
shelly, or pebbly character. The deep hole near 1,400 north by 600 east, and 
the deeper parts of the channel leading to the Outer Harbor, have a bottom of 


14 THE RELATION OF PLANTS TO TIDE-LEVELS 


sand and shell fragments which are shifted about by the swift current at each 
ebb and flow of the tide. The only plants discovered here are those of Ulva, 
Polysiphonia, Agardhiella, etc., which are drifting along and dragging with 
them the pebbles or shells to which they are attached. To the south and the 
east of this deep hole there is a considerable area of bottom below the 1-foot level 
that is covered with a decimeter or more of mud overlying the gravel and which 
is occupied pretty completely by Zostera. (See plate 1.) To the west of this 
depression lies the tide-channel that starts at the Research Laboratory. This 
channel has a bottom somewhat below —1 foot, with a mud bottom, which also 
bears more or less scattered Zostera. 

From the —1 foot level up to the lower margin of the Spartina at 1.5 feet 
practically the whole bottom is of soft brown or black mud. The only exceptions 
to this are the gravelly east shore of the Inlet, from 1,600 to 2,400 north, and the 
bed of the Creek, from 100 south to 400 or 500 north. The depth of the mud 
over the gravelly bottom which underlies the whole Inner Harbor, varies from 
a decimeter or two up to 1.5 or even 2 meters. The only plants really growing 
on or in this mud, aside from the diatoms coating certain areas, are Zostera, 
which gets above mean low water near 600 north by 500 east, and Ruppia, 
which ranges from mean low water up to +1 foot. The alge found growing here 
on scattered shells, pebbles, or sunken stakes, or on the living mussels, are 
really rendered thus quite independent of the nature of the bottom. The same 
thing is true of the floating tangles of Hnteromorpha and sheets of Ulwa. 

The character of the bottom from +1.5 feet up to about 6.5 feet is pretty 
constant about the whole harbor, except where changed by entering streams or 
artificially modified. These levels of the shore consist of a fine-grained, peat- 
like mud that is more or less firmly bound together by the living and dead 
rhizomes and roots of Spartina glabra, which forms a nearly continuous belt 
on all natural shores at these levels. The distribution of the Spartina, shown 
in plate 1, indicates that of this type of bottom. Only on recently formed 
gravelly shoals (e. g., near 200 north by 600 east) or at points where smaller 
entering streams have cut away this peat down to the underlying gravel, or 
where bathing beaches have been constructed, is this type of bottom wanting 
about the whole harbor. Along the south shore of the Spit from 800 west to 
400 east, it is true, as was noted earlier in the paper, that this peaty bottom does 
not reach quite down to the 1.5-foot level. The depth of this peat, which usually 
tapers out to nothing between the 6-foot and 7-foot levels, may be as much as 
from 3 to 7 dm. in the lower half of the Spartina belt. A series of soundings 
with an iron rod, along a north-and-south line at 10 west, showed a thickness of 
this layer which at first increased and then decreased in going shoreward from 
the 2-foot level, in the way indicated in plate v. Essentially the same thickness 
of peat covers the gravelly bottom on the east and west shores, as is shown by 
the actual sections of the peat cut by the rivulets entering the harbor over the 
upper beach (e. g., that at 1,650 north by 800 west). 

This layer of peat or peaty mud on which the Spartina flourishes is not of the 
same consistency throughout its thickness. The upper 2 or 3 dm. are firm and 
fibrous, while the portion below this is far more liquid, so that the upper layer 
shakes or quakes with the stamp of the foot. The living rhizomes never 
penetrate far into this less-solid lower layer, which is but little more firm than 


SUBSTRATA 1D 


the mud covering the bottom of the harbor. The upper, 7. e., inshore, edge of 
the peat belt becomes fairly well drained at low water, due largely to the number 
of burrows of the fiddler crab Gelasumus pugilator. Toward the middle and 
lower edge of the Spartina belt the soil is less firm and is poorly drained, except 
close to the edge of stream-channels and, in some places, along its own abrupt 
lower border, at the 1.5-foot level. In these places only do the fiddler-crab 
burrows, and an occasional muskrat burrow, afford some drainage and an 
opportunity for aeration. 

The only plants usually occurring on this peaty soil besides Spartina glabra 
are the alge Rhizoclonium, Enteromorpha clathrata, Fucus vesiculosus spiralis, 
and occasionally Lyngbyas, which are matted about the Spartina stalks or over 
the mud. Near the upper margin of this zone of soil, however, occasional 
inwandering seed plants from the higher levels may be encountered. Of these 
the most often found are Solidago sempervirens and Sueda. | 

On the gravelly soils of the stream-beds there occur Lileopsis at 3 to 5 feet 
Triglochin and Plantago decipiens near 6 feet, and the alge Hnteromorpha 
intestinalis, Monostroma, Ilea, and Hildenbrandia. 

The soil of the zone above the 6.5-foot level differs much more at different 
parts of the boundary of the harbor than that below this level, the character at 
each point depending apparently on the supply of fresh water and on the plant- 
covering of the same part of the shore just above high-tide level. 

On the Spit, e. g., the soils above 8 feet are sandy and dry. In correlation 
with this we often find between 6.5 and 8 feet a sandy or gravelly soil, with little 
humus, occupied by felts of alge or by Salicornia and Sueda. Trese gravelly 
and sandy stretches are perhaps due primarily to wave-action, for when the 
dead Spartina stalks have been broken off in the fall, the waves raised by the 
strong winter winds beat with considerable force against this south shore of 
the Spit. Alternating with these areas of gravelly soil stretches containing 
more humus are found, which are occupied chiefly by Spartina patens and 
INstichlis. 

On the shaded west shore, and on the east shore south of the mill, we find 
these levels, except for the narrow stream-beds, furnished with a damp, humus- 
containing soil that is sometimes very peat-like in character. This usually 
grades off insensibly below into the peaty substratum of the Spartina glabra. 
Above this there is often a sharp cliff-like drop at the boundary between the 
soil of this belt and the soil of the supra-littoral belt, near the 7.5-foot or 
8-foot level. At the bottom of this little escarpment, of a decimeter or two in 
height, the gravelly or sandy subsoil is often nearly bare of mud. The vegeta- 
tion of this soil of the upper littoral belt on the east and west shores consists in 
the better-drained areas, chiefly of Spartina patens, and where fresh water is 
present chiefly of Scirpus americanus. In with these are scattered Scirpus 
robustus (near fresh water), Solidago sempervirens, and, on more sandy areas, 
Spergularia (plates x1r and x111). Along the rivulets and streams plants of 
the supra-littoral belt may push down below the 8-foot level. 

Along the southern boundary of the harbor, at the north edge of the Marsh, 
the most marked change in the character of the soil in passing upward from the 
6.5-foot level is in the greater firmness and probably larger percentage of organic 
content of the soil, as it rises abruptly from the 6-foot to the 7-foot level and 
then slopes up very gradually to the 8-foot or 9-foot level. The upper layer of 


126 THE RELATION OF PLANTS TO TIDE-LEVELS 


soil on this gently sloping portion consists of 2 or 3 dm. of tough, black, fibrous 
peat, bound together by the dead and living rhizomes and roots of the Spartina 
patens, of Distichlis, and of Scirpus americanus, by which this part of the 
Marsh is chiefly covered. A study of the subsoil of this Marsh, by the aid of the 
section cut out by the Creek, as well as by several series of soundings made with 
an iron sounding-rod, shows that the firm superficial layer of the peat is under- 
laid by one of soft, black, peaty mud, of a thickness varying from 1 to 10 or 15 
dm. Beneath this is a layer of firm sand or gravel, with a very uneven upper 
surface, perhaps due to the covering up with the soft muck, of a delta cut by 
many channels. (See fig. 3, p. 111, which gives a north-and-south section at 
1,100 east, as reconstructed from soundings by Professor York and Mr. Paul 
Collins.) The muck below the surface here is, in consistency, much like that at 
the bottom of the harbor, and that underlying the firm surface peat of the 
Spartina border about the barbor. 

The soil of levels above high-water mark differs very greatly on different sides 
of the harbor. On the Spit, e. g., there are large areas where the surface layers, 
at least, are of nearly pure sand, only partially fixed by the tufts of Ammophila 
and occasional clumps of Solidago sempervirens. In depressions near the top 
of the Spit, however, e. g., near 500 east and 800 west, there are patches of firmer 
soil, rich in humus, and supporting a considerable variety of plants. In fact, 
wherever a tree or a group of bushes becomes established on the Spit humus 
accumulates and the soil 1s held together, so that such areas may be left standing 
considerably above the rest of the surface, which is lowered by the removal or 
sand by winds and waves. This is true, e. g., of the area about the Robinia near 
600 west, of that about the group of Ailanthus near 100 east, and of that about 
the group of hus at 540 east. 

The soil above the 8-foot level on the east and west shores of the harbor, 
aside from the gravelly artificial surfaces of the wharves, is not much affected 
by the proximity of the sea. In many places it is springy, wet, and shaded, 
and most of the plants on it are species found in inland wooded swamps, though 
Scirpus americanus does push up the streams to 9 or 10 feet. In drier, sunny 
places, beach-plants, such as Solidago and Atriplex patula hastata, may crowd 
up among the upland forms to as high as the 8.5 or 9 foot level. 

On the Marsh, as we have seen in Section III, the character of the soil and 
the vegetation changes rather gradually in going southward from the middle of 
the Marsh at 8 feet to the foot of the causeway embankment at 9.5 feet. These 
changes in soil and in plant-covering are indicated more precisely in the detailed 
maps of the Marsh (plates x1, xx1, and xx11). The relation of the vegetation 
to the substratum is too complex and the causes of its detailed distribution too 
incompletely understood to make it worth while to take it up in any detail again 
here, after what has been said earlier in this paper. 

In general summary of the relation of the distribution of plants to soils in 
the harbor, it must be considered as evident: (1) That the sparsity of attached 
algee on the bottom of the harbor must be due chiefly to the lack of larger 
particles in the soft mud to which plants like the rockweeds and red alge can 
become attached. Similar tidal basins in the neighborhood, having stony 
bottoms, show a much more varied algal flora (e. g., Center Island and Lloyd’s 
Point). (2) The peaty mud, commonly found between the 1.5 and 6.5 foot 
levels, is dominated by Spratina glabra, with only a subordinate ground-covering 


SUBSTRATA LAT 


of green and blue-green alge. Since, however, this Spartina grows luxuriantly 
in this neighborhood in nearly pure sand, it seems more probable that the Spar- 
tina determines the character of the soil rather than that the latter conditions 
the occurrence of the grass at these levels in our harbor, that is, the thick stand 
of salt reed-grass, between the tidal limits endured by it, favors the deposit of 
organic as well as inorganic sediment on the surface and also adds considerable 
organic material by the decay of its own roots and rhizomes within the soil. 
(3) In the case of the higher levels of the Marsh there seems to be a definite 
dependence of the character of the plant-covering on the salinity of the soil- 
water and on the depth of the peat-like layer of top soil. (See fig. 3.) While 
Spartina patens may grow from the 7.5-foot to the 8-foot level, in peat with 
soil-water of a salinity or specific gravity of 1.017+- at this same level, and in soil 
of otherwise the same character, except that the soil-water has a shghtly lower 
specific gravity, the plant-covering consists primarily of Distichlis. If near the 
higher level mentioned the salinity of the soil-water gets below 1.006, these two 
grasses are often replaced by Scirpus americanus. (4) The soil differences 
of most importance in their effect on plant distribution in the two belts between 
the 6.5-foot and the 12-foot levels on the north, east, and west sides of the Harbor 
are those in salinity of soil-water, and, especially on the Spit, differences in the 
amount of humus in the soil. 


2. SoLIp SUBSTRATA (STONES, PEBBLES, SHELLS, PILES, AND Logs). 

The most important of the solid substrata in our harbor are the pebbles of 
the natural bottom of the Inlet and the stone walls and wooden piles and 
docklogs of the wharves. The scattered stakes and the shells and occasional 
stones of the bottom are far less important as plant substrata, the one exception 
to this latter statement being the shells of living mussels mentioned earlier, with 
their hundreds or thousands of young plants of Ulva and Cladophora. 

The pebbles of the Inlet consist of well-rounded bits of quartz, granite, gneiss, 
sandstone, or conglomerate, of all sizes up to 1 or 2 dm. in diameter (plate 
xviIr). No adequate evidence was obtained of a marked preference of any of the 
algee for one material among these pebbles rather than another. The Chlorophy- 
cee, Hnteromorpha clathrata and Ulva, and red alge, such as Agardhiella, Chon- 
drus, Gracilaria, Hildenbrandia, and Polysiphomia, are found more commonly 
on the smaller, smooth, quartz pebbles, which make up the larger portion of the 
possible attaching surface on the bottom of the Inlet. The Phzophycee, 
Ascophyllum and Fucus, on the contrary, are usually found on the larger, rough- 
surfaced bits of granite or sandstone. It is probable that with the growth of the 
plants of the rockweeds that happen to start on smaller pebbles the supports are 
ultimately dragged away by these plants and thus either washed upon the beach 
or buried in the mud of the bottom of the harbor. This may account for the few 
quartz pebbles found bearing Fucus or Ascophyllum. Ulva starting on these 
smaller pebbles may likewise grow and finally drag off the latter. In other 
cases if the pebble is firmly fixed among its fellows or is too large to be dragged 
away by the plant, the growing sheet of Ulva may be torn loose and float or 
drift about over the bottom. In fact, the incrusting alge, such as Calothriz, 
Ralfsia, and Hildenbrandia, which grow on the large stones as well as the small, 
the rough as well as the smooth ones, are the only species which may not finally 
drag off their supports if the latter happen to be small. 

9 


128 THE RELATION OF PLANTS TO TIDE-LEVELS 


The stone of the wharves about the harbor is chiefly a brown sandstone. There 
are, however, numbers of large blocks of granite and gneiss scattered among the 
brownstones of the wharf on the east side, from 1,000 north to 1,600 north. 
Certain yellowish blocks of this granite and gneiss are constantly bare of 
Ascophyllum and Fucus, though all the surrounding stones of otherwise similar 
character and the brownstone blocks are densely covered by these alge (plate 
111). As no differences could be discovered in the chemical or physical charac- 
ters of the barren and the alga-covered rocks (see p. 70), we have no explanation 
to suggest for the striking difference in their alga population. In speaking of 
the gravelly soils above the 6.5-foot level, we have mentioned that Calothriz, 
Lyngbya, or Microcoleus are attached to the surfaces of the pebbles of the upper 
littoral beach, forming “ Phycochromaceta ” of Warming (1909, p.175). These 
simple forms are attached to the surfaces of these fine pebbles and sand grains 
just as the larger alge of lower levels grow on the larger pebbles of the Inlet, or 
of the channels of fresh-water rivulets along the shore (plate x). 

The wooden channel-stakes of the middle of the harbor form, as was noted 
just above, a restricted but often densely populated substratum for numerous 
alge. Thus a single stake may bear, attached to its bark, or, in older stakes, to 
the bared wood, groups of tufts of Melosira, Navicula, Ulva, Enteromorpha 
clathrata, Ralfsia, Dasya, Grinnellia, and Porphyra, besides felts or tangles of 
Rhizoclonium mingled with various blue-green alge. On the larger piles and 
wharf-logs and on bits of heavy wreckage along the shore, the algal population 
may be much richer in both individuals and species. Thus, e. g., the vertical 
chestnut piles of the wharf of the Research Laboratory may bear a dense drapery 
of rockweeds, any gaps in which are largely occupied by felts of Lyngbyas and 
Rhizocloniums, by warty incrustations of Ralfsia, by an occasional Porphyra, 
or by dense colonies of Bostrychia. In the winter Ulothrix flacca becomes 
prominent on these same piles. Near high-water level occur bands of felted 
' Lyngbyas and tufts of Calothriz. All of these alge, except the finer-felted ones, 
are attached to the firmer parts of the wood, and careful study of sections of the 
holdfasts of Ascophyllum and Fucus, of Bostrychia and Porphyra, show that 
these do not really penetrate into the tissue of the wood, but simply spread over 
the surface and into the furrows between the harder strands of the wood. The 
wooden wharf-logs are generally too near high-water level to bear much rock- 
weed, but they often have an abundant felt or tangle of Rhizocloniwm even at 
the 8-foot level when on the north side or where the log is kept moist. At the 
8-foot level on logs and stones of the Research Wharf grew the only species of 
lichen found near high-water mark. This lichen, Lecanora subfusca, occurs 
also at this same level on stakes on the Marsh. 


2. THE INFLUENCE OF WATER-CURRENTS. 

Under this head are included the effects of water-movement in streams, tidal 
currents, and waves. Such water-currents may affect the distribution of plants 
directly, as by wafting about the plankton of the surface and the drifting plants 
of the bottom, or by the dispersal of the spores or seeds when shed. They may 
also cause injury or even the total destruction of plants on shores or wharves by 
carrying ice against them or dropping flood-trash upon them. On the other 
hand, these currents may affect plants secondarily, by determining either the 
character of the substratum, the different degrees of aeration of the water over 
different areas, and finally by a favorable or unfavorable effect on competitors. 


WATER-CURRENTS 129 


The plankton organisms, such as the Diatomacee and Peridinee, are often 
drifted together in certain corners of the harbor by tidal currents and winds till 
they color the water deeply, while other parts of the harbor are comparatively 
free from these plants. The distribution of many Chlorophycee and Floridee 
that are free or attached to small supports is changing constantly and they drift 
with the tide. The ultimate results of this drifting is often the stranding of 
these plants so high up on the bottom or shore of the harbor that they are 
killed by exposure. We have mentioned in detail in Section III (pp. 18, 21), 
the repeated redistribution of plants or fragments of Ulva and E'nteromorpha 
clathrata, and the same process must be very active in the case of Fucus vesi- 
culosus spiralts in late winter and early spring, when the wearing off of the dead 
stalks of Spartina by ice and waves has left the Fucus free. 

It is evident that spores or seeds discharged into moving water may be carried 
to very considerable distances by it. The seeds or spores of plants, e. g., those 
living in the tidal channels, must thus be distributed widely over most or all of 
the habitats suitable for them, as well as over many others. We suggested above 
(p. 32) that certain Floridex, of sporadic occurrence in the Inner Harbor, 
probably arise from spores which are brought in by the tide from neighboring 
areas in the Outer Harbor, where they are present year after year. A very 
interesting question that arises here, which can be answered by experiment only, 
is whether these spores can become attached to surfaces of stone, shell, or wood 
while the tidal currents are still running, or whether it is only for a short time 
at slack-water that an effective holdfast can be developed. The cases of alge 
like [lea and Monostroma, in streams near high-water level, are of especial 
interest in this connection, since the only period of slack-water in these habitats 
is that at high water, and then the pebbles on which the spores are to start are 
surrounded by salt water. The fresh water of the streams at this time, as was 
shown by Miss Streeter, runs out on the surface of the harbor, leaving salt water 
next the bottom.* It may prove true that the spores of these plants, which are to 
live most of the time in fresh water, do, and perhaps can, germinate only in salt 
water. If this is the case it would offer an interesting explanation of the fact 
that these alge do not spread up the streams beyond the high-water mark. 

In winter, when ice is abundant in the harbor, the plants of the shore, and 
especially the alge on the piles and walls of the wharves, are subjected to pretty 
serious grinding by the cakes of ice and may even be frozen into the ice during 
very cold weather and then torn off. Tufts of Spartina glabra, a meter square, 
were found in July 1910, many yards away from the nearest Spartina. In 
1910, e. g., the small tuft at 2,200 north by 750 west was a newcomer. The 
only plausible explanation we can offer of the appearance of this tuft in an area 
which in 1909 was totally bare of Spartina is that ice froze about the stalks of 
the plant at high tide, in early winter, and that later, with a higher tide, the 
clump of the grass, with the peat-mass on which it grew, was lifted bodily and 
floated by the ice to its present position. In this case the grass has persisted for 
two (or three) seasons. In other cases, where the turf is dropped in the middle 
of the harbor, 1. e., in deeper water, it does not flourish, probably because of too 


8 Our tests of the Creek at high water of an 8-foot tide showed the presence, just 
above the bottom, of a stratum of water about 1 foot thick with a density of 1.020 
which extended upstream to 600 south. A layer about 2 feet in thickness next above 
this had a density varying from 1.020 to 1.014. The water at the surface upstream 
from 450 south is entirely fresh, while from this point northward it increases in 
salinity to a density of 1.010 at 50 north. 


130 THE RELATION OF PLANTS TO TIDE-LEVELS 


great a proportionate submergence. The alge on the mud among the Spartina, 
such as Fucus vesiculosus spiralis (plate xv1), Rhizoclonium, etc., apparently 
suffer also from the winter waves, aided by the ice. At least they are relatively 
scarce in the early spring. 

On the banks of tide channels, e. g., on the west side of the Inlet, or on the 
concave banks of the Creek (near 100 south) the turfs of grasses are often under- 
mined by the swift current and many pieces fall into the water to be carried 
away. Large numbers of plants and very considerable areas of soil are thus 
destroyed. 

Another way in which tidal currents and waves may injure plants is by 
covering them with tide-trash so deeply as to smother them out. Instances 
in which Spartina glabra, S. patens, Salicornia, and other species are thus 
destroyed over areas of several square meters are mentioned in Section ITI. 

Of the secondary effects of water-currents on submerged plants, the most 
important is probably the effect of this movement on the concentration, in the 
water about the plant, of solutions of useful and injurious gases or solids, and 
on the rate of interchange between the plant and the immediately surrounding 
water. It is a well-known fact that the hard bottoms of swift-flowing tide- 
creeks, or bottoms just below low-tide mark on wave-beaten shores, have an 
unusually luxuriant algal flora. While this is partly due to the stony bottom 
found under swiftly moving water, yet it is evidently attributable partly to the 
effect of the agitation of the water on the plants themselves. It is probable that 
all of the effects above mentioned are of importance. But no one, so far as we 
know, has yet proved experimentally whether the movement of the water is 
more important in simply increasing the rate of interchange of material between 
the plant and the surrounding water, or in bringing to the plant solutions of 
substances needed by it and removing waste substances cast off from it. The 
action of the waves in floating out the tangles of rockweed of the mid-littoral 
‘belt, and of then keeping them in almost constant motion, indicates that both a 
better aeration of the water and a higher rate of interchange of nutrient and 
waste substances between water and plant must result. These would be very 
interesting points to settle definitely by carefully checked physiological 
experiments. 

The influence of water-movement on a plant may also be exercised second- 
arily through the favorable or unfavorable effect of this movement on its 
competitors. For example, it is evident that the inability of large sheets of 
Ulva to withstand the strong current in the Inlet prevents the huge sheets of 
this species from covering large areas of the bottom here, as it does in the 
quieter parts of the Inner Harbor, and thus prevents it from smothering out 
many of the species that now find congenial conditions in the Inlet. On the 
other hand, the drifting by the tide of the rolls of Ulva mentioned on page 20, 
and the final settling of these on patches of Zostera and Ruppia, may smother 
these latter out in the same way that the masses of Ulva, Enteromorpha clath- 
rata, or of other tide-trash, have been shown to smother Spartina glabra, and the 
algal felts with it, in the mid-littoral belt. It is probable that it is the inability 
of other brackish-water alge to gain, or maintain, a foothold in such a swift 
current that gives Ilea fulvescens such undisputed sway on the steeper pebbly 
bottoms of the Creek between 150 south and 500 south. 


TIDAL CHANGES Fel 


3. THE CHARACTER OF TIDAL CHANGES AND THEIR INFLUENCE ON 
PLANT DISTRIBUTION. 

In the earlier sections we have repeatedly referred to various effects of the 
tidal changes in water-level on individual species of plants. We may now look 
more closely into the magnitude of the tidal changes in water-level and the ways 
in which the latter may affect the growth, and other physiological activities, of 
littoral plants, and thus aid in determining their distribution. These peculiari- 
ties and effects of the semi-daily rise and fall of the tide may be discussed under 
the following heads: (A) Characters of the Tides; (B) Effect of Tidal changes 
on Evaporation; (C) Effect on Aeration; (D) Effect on Salinity of Soil-Water 
at High Levels; (EK) Effect on Exposure to Rain; (F) Effect on Light Supply. 

In addition to the effects just enumerated the tides cause part of the water- 
currents that are referred to above and also have an influence on the salinity and 
the temperature of the water of the harbor in general, which are to be discussed 
below. 

A. CHARACTER AND MAGNITUDE OF THE TIDES. 


The predicted, semi-diurnal range in water-level, due to tides, varied during 
the growing season of 1911 from 4.2 feet to 10.8 feet. (See plate xxiv, and 
Tittman, 1910.) The “mean range” during this season was 7.63 feet. This 
mean range varies from year to year, and the one here given for the growing 
season of 1911 is about 0.1 foot below the “ corrected mean range” for three or 
four decades. 

The smaller or “ neap range” occurs just after the first and third quarters 
of the moon in each month. This neap range varied, during the months from 
May to October 1911, from 4.2 feet on October 1 to 7.0 feet on June 20. The 
greater or “ spring range” occurs just after the new moon and the full moon. 
This varied in 1911 from 8.5 feet on July 14 (and 8.6 feet on June 10) to 10.8 
feet on May 27. (It was 10.7 feet on October 10 and even 11 feet on April 30, 
the day before the beginning of our somewhat arbitrarily fixed growing season.) 
These various facts are indicated graphically in plate xx1tv. The chart there 
shown was constructed from data given in the U.S. Tide Tables above referred 
to. (See also tables A, B, and C, pp. 135, 136.) 

Of course, the high water actually occurring at Cold Spring Harbor may 
sometimes be higher than that predicted, because of a northerly wind blowing 
the water into this long, narrow harbor. Or on another day high water may be 
lowered by a southerly wind retarding the inward flow of the water at flood-tide. 
On the other hand, the height of a low tide may be lowered: by a strong 
southerly wind or kept above the predicted height by the retarding effect of a 
northerly wind during ebb tide. In the long run, however, this influence of the 
wind in modifying the water-level at high and at low tide would prove about 
equal in both directions, and so the actual tides would show an average or mean 
range corresponding closely with that of the predicted tides. It must be 
remembered that any effect of a general prevalence of winds from one direction, 
é. g., from the southwest in summer, is one of the factors included in the actual 
tides observed at Cold Spring Harbor in 1894, on which observations the 
prediction of tides for this station is based. 

The general effect of the semi-diurnal variation of water-level, with high and 
low tides, on the vegetation of the shores, is probably dependent (see p. 14 


1382 THE RELATION OF PLANTS TO TIDE-LEVELS 


above) chiefly on the average or mean range of the tides from end to end of the 
growing season. For plants growing just below mean low water or just above 
mean high water it is probable that the occasional extremely. low tides or 
extremely high tides may be of great, possibly of preponderating or critical, im- 
portance (see p. 15 above). We shall look into this latter question in more 
detail later on. 

It is evident that the direct primary effect of this oscillation of the water- 
level, twice each “lunar day” of 24.9 hours, will be the twice repeated sub- 
mergence by the water and exposure to the air of all plants growing between 
tide-marks. While the roots and submerged portions of the shoot are under 
water they are wholly or partially shut off from the light and completely shut 
off from a supply of air, except as this may be conveyed to them from the exposed 
portions or absorbed from the submerging water. ‘The possible secondary effects 
of this submergence and exposure we shall attempt to analyze later on. 

The determination of the exact time of submergence and exposure of soils 
and plants at the various levels necessitates carefully made and recorded 
observations of the rate of rise and fall of the tide. Since no such data for the 
Inner Harbor at Cold Spring Harbor were available, measurements were made 
in the manner described on pages 12 to 14 above. These measurements are 
expressed in the curve shown in plate v1, which was briefly described earlier in 
this paper (p. 13), in order that the data embodied in it might be used in the 
discussions in Section III. 

The chart referred to gives the curve for two successive tides of a single lunar 
day. ‘The tides chosen are of about mean range. From this chart the sub- 
mergence and exposure, by an average tide, of all levels of the shore between 
mean low water and +-7 feet, might be determined. But in order that the aver- 
age submergence and exposure during the growing season of these levels, and of 
levels lower and higher than these, might be determined, records of all tides, 
‘from May to October, were needed. Since we were unable to make these by 
actual measurement at Cold Spring Harbor, recourse was had to the records of 
actual tides, and especially to the predicted tide curves, for Willet’s Point, New 
York. This is the nearest tide-recording station of the U.S. Coast and Geodetic 
Survey and is the “ standard port for reference ” for Cold Spring Harbor. An 
actual recorded curve for Willet’s Point for July 18, 1894, is shown in the chart 
in figure 4.° This shows the form of curve for a tide of mean range. This curve 
has the general form of that for the tide of mean range at Cold Spring Harbor, 
though it shows a slight flattening at the top, and a striking retardation in the 
rate of fall of the water-level just before mean low water is reached. Plate xx11I 
shows a portion of the “ predicted tide curve ” for May 1911, made by the tide- 
predicting machine of the Coast and Geodetic Survey. 

In these predicted curves for tides at Willet’s Point those for mean tides 
show a close resemblance to the curve of the actual mean tide at Cold Spring 
Harbor. We may, then, assume, what is highly probable, that the curves of 
actual tides of neap range and of spring range at Cold Spring Harbor would 
resemble in general those for the same tides at Willet’s Point, just as the curves 


*The writers are greatly indebted to Mr. O. H. Tittman, Superintendent of the 
Survey, for his kindness in having the curves of actual tides traced and in having 
the predicted curves, for the season from May 1 to October 31, 1911, made anew 
for us, by the new tide-predicting machine of the Survey. 


JOHNSON AND YOR PLATE XXIII. 


Feet ; 
9 Predicted tide q 
4 May Ist-5th.19 
7 2 








Mean sea level. ay 3rd. 
iSe20 21 








19bL 


the day 





JOHNSON AND YORK. 



































































PLATE XXIll. 
Feet . : 
9 Predicted tide curve 
3 May Ist-Sth. 1911. 
/ 
7 / LEE as 
6 
5 
ib 
4\— Mean sea level May1,ISI! ___Mean sea level. 
3 Ruretio 2. Asp RTS 96 oy © 6) & io “I 12-213 me ies Jame 8 19 aD Wie tan eee is 19 20 2 22 
2 
ip y * 
0 Mean low water ee * os a 
_ Sa 
=F 
Feet 
9 
8 
7 —— I 
6 ~ ee 
E : * aA 
: \ ye \ 
4 eee , May! 4th. ig h Mean sea level / : May 5th. 
3 : Soe eat] ai Ea ae eae 7 ps) DE GE | Mac SG Wee cs on i chee eo a PEN 0) Eee Gulia oS, 9> 10 Me 
> / 
SS 
, Mean low water Ss 25 we 


Curve Suowrne Portion oF THE PREDICTED TIDE CURVE FOR WILLET’s Point, N.Y, For May 1911. 


Made by the tide predicting machine of the U. 8. Coast and Geodetic Survey, on March ikfi, TSB 
This curve shows the form of the curve for tides of different range, also the marked difference in range of the day 
and night tides of the same lunar day. 


SUBMERGENCE AND EXPOSURE ino 


of actual mean tides at the former station were found to resemble those for the 
same tides at the latter station.* 

If, then, we allow for the 0.4 foot greater height of high water at Cold Spring 
Harbor, we can, from this predicted curve for Willet’s Point, determine with 
sufficient accuracy the probable duration of submergence and of exposure of any 
level between tide-marks at Cold Spring Harbor. That is, we can determine 
by measurement, between the points of intersection of the horizontal line 
representing any level with the curve, the submergence and exposure of that 
level per lunar day per month, and so the total for the whole season of six 
months. 

Table A, page 135, gives the duration of submergence and emergence, per 
lunar day and per average calendar month, for various levels from —1.25 feet 
to +9.00 feet measured from this predicted curve. This table shows in the 
second and third columns the average total submergence in hours per month of 
each level. The emergence of levels below mean low water and the submergence 


N00 RC SO 


 - ON Ae ee 
a a a 
ee Na 
INEM TR Gs RG A Pe Se 

mmm tL 
Oe a EE a SC a 2 Ve 
EET SS 7 Fe TE 


0 
Time IZPM. 1AM. 24M. 3AM. 4AM. SAM. 6AM. 7A.M. BA.M. 9AM, IOA.M, A.M. 12M. 12M. 2PM. 32M. 4PM. SPM. 6PM. 72M. SPM. OPM. IORM, HRM, 122M. 







Fic. 4.—Chart of tidal-curve of two successive mean tides, recorded at Willet’s 
Point, New York, on July 18, 1894 (supplied by the U. S. Coast and Geodetic Survey). 
(In comparing this curve with that in plate XIV note that the horizontal unit of the 
scale, representing an hour of time, is 20 per cent greater than the vertical unit, 
representing a foot in height, instead of equal to it, as in plate XIV. This accounts 
in part for the greater flattening of the crest and hollow of the curve.) 


of levels above 6.5 feet was measured on the predicted curve for Willet’s Point 
for all tides of the season. In determining the submergence and exposure of 
levels from 5 feet upward, allowance was made for the greater height of high 
water at Cold Spring Harbor, by measuring the submergence for each level at 
0.4 feet lower down from the crest of the curve of the tide for that day, or by 
measuring it on the curve of a tide of proper height, though it happened to be 
on another day. The durations so obtained when divided by 6 give the average 
durations of submergence or emergence for each month of the growing season. 
The submergence of the lower levels was obtained by subtracting the total 


* Actual records of the tides of the Inner Harbor at Cold Spring Harbor were made 
with a tide-gage loaned by the U. S. Coast and Geodetic Survey, in July, August, and 
September, 1913. The form of this curve corresponds very closely with the con- 
structed curve shown in plate v1 and with the predicted tide-curve for Willet’s Point. 
The most striking peculiarity of the curve recorded at Cold Spring Harbor in 1913 
is the sharpness of the trough at low water. This probably means that the times of 
“ihe given on page 136, for plants growing near mean low water are slightly 
too large. 


134 THE RELATION OF PLANTS TO TIDE-LEVELS 


monthly emergence from 736.5, the average total number of hours in each 
month. The emergence for the higher levels was obtained by subtracting the 
monthly submergence from the average number of hours in a month. The 
exposure of any level varies greatly, of course, from month to month. Thus, 
e. g., the —1-foot level was not exposed at all in August 1911, while its probable 
emergence for May was 9.5 hours. Again, the probable submergence of the 8.75- 
foot level for August 1911 was 0.0 hours, while for May it was 11.25 hours. 

The average monthly emergence of levels between mean low water and 3 feet 
was obtained by measurement on the predicted tide-curve for Willet’s Point for 
August, since the mean low water for this month (0.038 foot) was closest to that 
for the whole six months of the growing season (0.006 foot). The submergence 
of levels between 4 feet and 6.5 feet was obtained by measurement on the 
predicted curve for June 1911, since the average high water for this month was 
exactly that for the season (7.63 feet). 

The fourth and fifth columns of Table A show respectively the average 
emergence and submergence per lunar day of 24.88 hours, there being 29.6 lunar 
days per month, or 177.5 lunar days per growing-season. From these data, or 
those for the month, the total emergence or submergence for each of the 59 tides 
per month (average) or 355 tides per season can be obtained. 

The sixth column of Table A gives the ratio of emergence to submergence for 
each level. These figures will be of value when discussing the upper and lower 
limits of plant distribution (see Section VI), since from them we can see the 
proportion of submergence to emergence endured by any plant at its upper or 
at its lower limit. 

Another series of tidal data of interest in connection with plant distribution 
is that concerning the frequency of submergence or emergence respectively of 
levels near the upper margin and the lower margin of the littoral region. From 
- the predicted heights of the low waters and of the high waters for each tide of 
the season, given in the United States Tide Tables for Cold Spring Harbor, it is 
possible to determine exactly the number of tides each month, or the total num- 
ber per season, in which any level near high-water mark will probably be 
submerged, or any level near low-water mark will probably be exposed, the only 
uncertainty in these cases being the possible effect of the wind in making the 
level attained higher or lower than that predicted. 

Table B (p. 186) shows the number of submergences per month and per 
season (May to October) of levels from 6 to 9 feet. These numbers were 
obtained directly from the Tide Tables by adding the 0.4-foot correction to the 
predicted high waters for Willet’s Point for each tide of the growing season. In 
connection with these numbers it should be recalled that there are 355 tides per 
season, which includes 58 each for June and September, 59 for October, and 60 
each for May, July, and August. From this table of infrequent submergences 
can be deduced the duration of the longer continuous emergences of these high | 
levels. 

Table C (p. 186) shows the number of emergences per month and per season 
of levels between —1.25 feet and +1.75 feet. These figures, like those in Table 
B, are taken from the heights of predicted low waters for Willet’s Point, which 
are in this case identical with those for Cold Spring Harbor. From the 


SUBMERGENCE AND EXPOSURE 185 


frequency of emergence of each level here given the duration of the longer 
submergences of these low levels can be obtained. 

From Tables B and C it is evident that the — 1-foot level and all below it may 
be continuously submerged for a month at a time, e. g., during August. Even 
the 0-foot level may, as can be seen from the Tide Tables, be submerged con- 
tinuously for from 4 days at a time, in May, to 7 days in June or August. On 
the other hand, the higher levels may be exposed continuously, never being wet 
by the tides, for many days together. Thus, e. g., in 1911, the 8-foot level was 
continuously exposed for 10 days in June, or even 12 days in July. Even the 
7.5-foot level may be exposed continuously for 4 days at a time, in June, or 
even 7 days, as from August 30 to September 6, 1911. For levels above 8 feet 
the duration of continuous exposure would evidently be markedly greater. These 
unusual tides which submerge the higher levels and expose the lower ones are 
grouped in two series each month, 1. e., at the two periods of spring tides. This 
fact is of great importance to the plants growing at these levels. It means that 
plants at the —1-foot level, e. g., may be constantly submerged for a month at a 
time and then, after three or four periods of exposure, of from half an hour to 
an hour per tide, they may again remain submerged for a fortnight or a month. 
So far as enduring submergence is concerned, this is probably equivalent for 
the plant to constant submergence. The plant is, however, obliged occasionally 
to withstand the exposure to sun and wind. In fact, even such a brief exposure 
may be of critical importance in limiting the upward extension of a delicate 
species. 

With so much of general discussion of the tidal changes themselves, we may 
now turn to take up their effect on plants. 


TABLE A.—Duration of submergence and exposure, from May 1 to October $1, 1911. 








1 Max, 5.5; min. 0.0. 


2 This means that this level is exposed only z}, 
as long as it is submerged. 


3 Max. 9.5; min, 5.0. 





4 Max. 34.50; min. 12.5. 
5 This means that this level is exposed 353 time 
as long as it is submerged. 


6 June. 


7 Season. 


- AON Sabo pear owe Average Average Ratio. 
Level. Average per cal-| Average per cal: eed Se ob ae Sale Emergence. 
endar month. | endar month. | P&* *U24 Gay. | per lunar day. Submergence. 

Feet Hours. Hours Hours. Hours. 

—1.25 1.66 1 734.84 0.06 24.82 1.66/734.84= 0.0023 2 

—1.00 3.70 3 732.80 0.12 24.76 Bat MponOE= OUD tL 

—0.50 23.50 4 713.00 0.79 24.09 23.0 /113.0 = .0816 
0.00 53.70 682.80 1.82 23 .06 ~53.7 /682.8 = .0788 

+0.50 112.75 623.75 3.80 21.08 112..75/624.0 = .1791 

+1.00 180.40 556.10 6.10 18.79 180.4 /556.0 = .38244 
1.50 239 .25 497 .25 8.08 16.80 239).2/497.2°=  .4807 
2.00 261.25 475 .25 8.83 15.95 261.2 /475.2 =  .65500 
3.00 338.75 397.75 11.07 13.81 338.7 /397.7 = .852 
4.00 397.50 339.00 6 13.43 11.45 397°5°/339.0 =" 1.172 
5.00 461.50 275.00 15.59 9.29 461.5 /275.0 = 1.674 
6.00 533 .62 202.88 18.03 6.85 533 .62/202.88= 2.625 
6.25 559.50 177.00 18.55 6.33 559.5. /177.0 = 93.161 
6.50 575.50 161.00 19.44 5.44 575.5 /161.0 = 3.574 
6.75 601.50 135.00 20.32 4.56 601.5 /185.0 = 4.455 
7.00 639.50 97.00 7A UB f 2.67 639.5 / 97.0 = 6.593 
7.50 689.30 47.20 23 .28 1.60 689.3 / 47.2 = 14.60 
8.00 706.14 80.367 23 .86 1.02 706.1 / 30.4 = 23.26 
8.25 719.70 16.83 24.31 57 719.7:-/ 16.88= 42.76 
8.50 727.80 8.70 24.59 .29 127-8: fe Sal == 8S..65 
8.75 731.86 4.64 24.78 -16 731.86/ 4.64=157 51 
9.00 734.42 2.08 24.81 .07 734.42/ 2.08=853.09 5 


136 THE RELATION OF PLANTS TO TIDE-LEVELS 


TABLE B.—Number of submergences per calendar month and for the season, from 
May 1 to October 31, 1911. 
{In each column, under the name of the month (or the season), the figures give the number of times that 
the level in question is submerged during that month or during the season.] 


Lével May. June. July. Aug. Sept. Oct. Season. 
* | (60 tides.) (58 tides.) (60 tides.) (60 tides.) (58 tides.) (59 tides.) | (355 tides.) 


Feet Times. Times. Times. Times. Times. Times. Times. 
6.00 60 58 60 60 55 58 351 
6.25 60 58 60 56 52 57 343 
6.50 60 58 60 54 52 53 337 
6.75 59 58 54 51 43 46 3ll 
7.00 52 54 52 44 43 39 284 
7.25 39 39 44 37 87 33 229 
7.50 33 33 38 34 So 30 200 
7.75 26 24 28 28 26 23 165 
8.00 23 14 21 22 21 20 121 
8.25 11 7 6 12 15 14 65 
8.50 8 5 3 2 5 ff 30 
8.75 7 4 0 0 3 4 18 
9.00 5 0 0 0 1 4 10 





TABLE C.—Number of exposures per calendar month and for the season, from May 1 
to October 31, 1911, of levels from—1.25 feet to 1.75 feet. 





May. June. July. Aug. Sept. Oct. Season. 
(60 tides.) (58 tides.) (60 tides.) (60 tides.) (58 tides.) (59 tides.) | (355 tides.) 

Times. Times. Times. Times. Times. Times. 

1 0 0 0 3 9 

3 2 0 3 4 17 

9 6 14 17 17 79 

26 27 28 28 27 165 

48 52 43 40 36 264 

58 60 55 48 46 323 

58 60 59 53 53 343 

58 60 60 56 55 348 

58 60 60 58 59 355 





.B. EFFECT OF TIDAL CHANGES IN WATER-LEVEL ON EVAPORATION OR 
TRANSPIRATION FROM THE PLANT. 


It is, in the first place, clear that when delicate, thin-cuticled plants like 
Zostera or Ulva are exposed at low tide during a warm, sunny day, they may be 
subjected to a dangerous desiccation. This desiccation, to which plants grow- 
ing above mean low water are liable, is undoubtedly concerned with determining 
the upper limit of distribution of such species. 

As has been mentioned in Section III, many plants of Cladophora, Entero- 
morpha, and Ulva, of various red seaweeds, and the leaves of Zostera, are often 
killed off by drying out on hot days in summer. The Ulva is oftenest destroyed 
by being floated to the higher levels of the beach by the air bubbles that collect 
under it on a hot day. 

We have spoken also (p. 91) of the drying out, and cracking to polygonal, 
tile-like blocks, of the felts of Schizophyceew and Chlorophycee occurring on 
the south shore of the Spit, between the 6.5 and 7.5 foot levels. At slightly 
higher levels these felts are usually wanting, probably chiefly because they and 
the soil bearing them are less frequently wet by the high tides, but are exposed 
to desiccation for a longer time. That the relative dryness of these higher levels 
really determines the absence of these algal felts seems clearly indicated by the 
fact that these felts may occur above their usual level when on the north or 
shady side of tufts of grasses, e. g., at 7.5 to 8 feet, on the top of the stone pier 
on the eastern shore. 


PLATE XXIV, 





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PLATE XXIV, 


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Crart SHOWING THE VARIATION IN RANGE oF TIDES THROUGHOUT THE GRowING SEason, CoLp SPRING HARBOR, 
FROM May 1 to OcrosBer 31, 1911. 


Tables, for Cold Spring Harbor. In the cases of May and June the varying degrees of coincidence of low tide with the 
hours of darkness and daylight are indicated by black bands for night and light ones for daytime. From this can be 
of time during daylight that plants at any level are above water. 


Oo 


MLW 


MLW 


TIDES AND EVAPORATION 137 


For the alge growing on the vertical stone walls and piles of the wharves, also, 
the upper limit of distribution is evidently determined by the amount of desicca- 
tion the plants can withstand. We have seen, e. g., (pp. 65 and 67) that 
Rhizoclonium and Fucus go highest in crevices in the wharf, or on the north 
sides of piles, where not reached by the sun and by winds. 

In like manner, for erect-growing seed plants between tide-marks, like 
Spartina glabra, the elevation attained is evidently conditioned, at least in part, 
by the desiccation it is subjected to. That is, by the length of time at each tide 
that its leaves are exposed to the dry air. A clear indication that this is the case 
is found in the fact that on certain shaded areas with moist soil on the western 
shore, this grass grows at a level much above its usual upper limit. It displaces 
here its sun-loving competitor Scirpus americanus, which as usual holds sway at 
these higher levels on adjoining dry and sunny portions of the shore. That a 
grass with rather thick-cuticled, rolling leaves should be en- 
dangered by the amount of transpiration it can be subjected to 
just above the 6.5-foot level, while its rhizomes and roots are em- 
bedded in a practically saturated soil, seems surprising at first 
thought. But it is to be remembered that the humidity of the air 
about the upper half of the plant, which includes most of the 
well-developed leaves, may be quite low. This is especially true 
of the south shore of the Spit, which is just where the upper 
boundary of the Spartina is strikingly definite. 

That attempt was made to determine the evaporating power 
of the air in this habitat of Spartina on the Spit, and in several 
other typical habitats by means of a porous-cup atmometer. For 
this purpose three atmometers were used, whose coefficients of 
correction had been determined by comparison with a Livingston 
standard atmometer. All the readings here given are corrected 
readings, and may therefore be directly compared with the Liv- 
ingston standard. 

For use at levels where, because of the danger of submergence 
by the tides, exposures can be made for only a few hours at a time, 
except occasionally during a series of neap-tides, an atmometer is = Fi. 5. 
required which will indicate very small losses of water. For this i tetera 
purpose the porous cup was attached to the shorter arm of a tige-marks. 
U-tube, the other arm of which was graduated to tenths of a 
centimeter by filling from a burette. The resulting instrument (fig. 5) is a 
simplified form of that described by Livingston 1906. Three instruments of 
this kind, which we will designate as Nos. 1, 2, and 3, were run simultaneously 
for a week in an instrument shelter, to discover possible leaks and to check up 
their relative rates. 

_ For three days in August 1909, during a series of neap tides, the three 
atmometers were exposed in different places and simultaneous readings made at 
the beginning and the end of each of the following periods: August 6, 11°00" 
a. m. to 12°40" p. m.; August 7, 7°20" a. m. to 12°20” p. m., and August 7, 
12°20” p. m. to August 8, 7°30" a.m. The total exposure for each instrument 
was 25.8 hours. The days on which the exposures were made were clear. The 
temperature recorded by a Friez thermograph in the shelter ranged from 18° 





188 THE RELATION OF PLANTS TO TIDE-LEVELS 


to 30° C., while the humidity recorded by a Friez hygrograph in the same place 
varied from 50 to 95 per cent. Atmometer No. 1, in the shelter, showed an 
average corrected rate of loss of 0.43 ¢.¢. per hour. It showed a minimum rate 
of 0.37 c.c. per hour in the period from 12"20™ p. m. August 7, to 7°30" a. m. 
on August 8, when the temperature ranged from 18° to 30° C., averaging 23.5° 
C., and the humidity ranged from 50 to 95 per cent, averaging 79 per cent. The 
maximum rate for this instrument of 0.75 c. c. per hour was shown on August 7 
from 7°20" a. m. to 12°20” p. m., when the temperature ranged from 21° to 27° 
C., averaging 22.2°, and the humidity varied from 53 to 75 per cent, averaging 
69 per cent. 

Atmometer No. 2, placed in a dense stand of Spartina glabra at 2,750 north 
by 290 east, with its cup at the 7.5-foot level and about 1.5 feet above the soil, 
gave an average corrected rate for the whole 25.8 hours of 0.79 c. c. per hour. 
The minimum rate at this station was shown for the period from August 7, 
12°20” p. m. to August 8, 7°30" a. m., the temperature and humidity in the 
shelter for this period being those given above. This corrected minimum rate 
was 0.67 c.c. per hour. The maximum rate for No. 2 of 1.1 c. c. per hour was 
also shown in the same period and under the same conditions as the maximum 
for No. 1,7. e., on August 7, from 7°20” a. m. to 12°20™ p. m. 

Atmometer No. 3 was placed 10 feet south of No. 2 among the stems of 
Spartina, in a reclining position, with its cup 4 inches above the soil and at 
about the 6.3-foot level. The corrected rate of this instrument varied from 0.36 
c.c. per hour to 0.63 c.c. It is interesting to note that the relative rate of this 
instrument varied from 0.5 to 1.7 times that of No. 1. This wide difference in 
rate of two instruments exposed simultaneously is probably due to the differences 
at the station for No. 3 in the direction and strength of the wind, and especially 
to the different amounts of water, from the preceding high tide, left clinging to 
_ the Spartina stalks at the beginning of the exposure. 

The amount of this adhering water would depend on the length of time since 
the tide receded from that level; also on the temperature and on the direction 
and strength of the wind, which might dry it off. It must be borne in mind, 
however, that the variations in evaporating power of the air here mentioned are 
entirely characteristic of locations between tide-marks, and are therefore real © 
factors in the environment of plants, which, like the alge on the mud and on 
stalks of the Spartina, live in these habitats.. 

Another series of records was made in which atmometer No. 1 was placed in 
the shelter, No. 2 was placed on the vertical stone wall, facing east, at 200 north 
by 80 west, near the 6.5-foot level, and thus near the upper edge of the rockweed 
belt, and No. 3 was placed at this same level on the north-facing wall at 10 south 
by 40 east. The three atmometers were exposed simultaneously during a total 
of 32.7 hours of daylight from July 27 to 30, 1909, in clear weather, while 
the temperature ranged from 22.8° to 34.4° C. (averaging 28° C.), and the 
humidity varied from 39 to 87 per cent (averaging 60 per cent). 

The record of No. 1 under these conditions showed an average corrected rate 
of 1.08 c. c. per hour (ranging from 0.89 to 1.56 c.c. per hour) ; No. 2 gave an 
average rate of 0.9 c.c. per hour (ranging from 0.5 to 1.16 ¢.c. per hour) ; 
while in No. 3 the rate averaged 0.72 c.c. per hour (ranging from 0.59 to 1.14 
¢e.c. per hour). 


TIDES AND EVAPORATION 1389 


Other series of atmometer records were started, but, because of accidents or 
lack of time, were not made complete enough to be of significance. 

From what has been said it is evident that the maximum rate of evaporation 
of 1.1 c.c. per hour recorded in the middle of a moderately warm day, by 
an atmometer among the leaves of the Spartina glabra, indicates that these 
plants are at times subjected to a relatively high rate of evaporation. If we 
multiply this hourly rate by 168 we get a weekly rate, 185, that closely ap- 
proaches the highest average weekly evaporation-rate, for the growing-season, in 
the United States east of the Mississippi, given by Livingston (1911, p. 219). 
Kven the average hourly rate for atmometer No. 2 in the Spartina, which 
included one night in the total exposure of 25.8 hours, was 0.79 c.c. per hour, 
or 133 c. c. per week. This considerably exceeds the average weekly evaporation 
for the summer at New York City, as given by Livingston (1911, p. 213), and 
the weekly rate of 95.5 c.c. at 2 meters above the soil found by Fuller (1912, 
p. 426) in a mesophytic beech-maple forest of Indiana. In fact, it very closely 
approaches that given for Salt Lake City (Livingston, p. 210). It nearly 
equals also the average rate of 0.83 c.c. per hour given by Transeau (1908, p. 
219) for his standard instrument, established in an open garden at Cold Spring 
Harbor. The rate of atmometer No. 2 in the Spartina for the period that 
included the afternoon and the night of August 7, was 0.67 c.c. per hour or 
113 c.c. per week. This indicates the correctness of Transeau’s suggestion 
(1908, p. 227) that the low average rate of evaporation from his atmometer, 
placed at the 12-foot level, on top of the Spit, in 1907, was due to the very slight 
evaporation occurring there at night. | 

The rate of instrument No. 2, when placed on the wall of the wharf, amid the 
rockweed, against stones saturated by water, and only 5 feet above the muddy 
bottom, with its trickling rivulets, averaged 1.08 c.c. per hour, or 181.5 c.c. 
per week, while its maximum rate reached 195 c.c. per week. This indicates 
the high rate of evaporation to which the rockweeds, Rhizoclonium, Bostrychia, 

and the Schizophycee of the wharves may be subjected, during low tide. These 
_ rates in fact approach the rate for the area about Lake Erie (200 c. c. per week), 
which is the highest average weekly evaporation-rate given by Livingston (1911, 
p. 219) for any part of the United States east of Texas or the Dakotas. 

It is, of course, realized that the few atmometer records here given can be con- 
sidered adequate to do little more than indicate the importance of this evapora- 
tion-rate as a feature of the environment of shore-plants living between tide- 
marks. To get a really adequate idea of the importance of this factor in the 
environment of plants growing at any level, we must have records by quick-regis- 
tering atmometers exposed at that level from the moment it is bared by the fall- 
ing tide until it is just about to be covered by the rising tide. Moreover, readings 
must be made each hour or half hour of all exposures, night and day, from end 
to end of the season. When this is done, as it is hoped it may be soon at Cold 
Spring Harbor, it is believed that both the average rate, and, in some cases 
especially, the maximum rate of evaporation in their habitats will be found to 
be intimately concerned in determining the upper limit of distribution attained 
by many of the species growing between tide-marks. 


140 THE RELATION OF PLANTS TO TIDE-LEVELS 


C. EFFECT OF TIDAL CHANGES ON AERATION. 


It is pretty certain that for thick-cuticled plants like the Spartina, Distichlis, 
Salicornia, Sueda, etc., the period of submergence at high tide is one during 
which there can be little interchange of gases between these plants and the sur- 
rounding medium. At this time the stomata of the shoot are closed by water 
and, during the whole time of submergence, the only supply of O and CO, 
available for the plant is probably that held in the air-canals of the shoot. In 
the case of Spartina glabra this stored supply occupies a considerable portion 
of the bulk of the shoot. The whole system of subterranean rhizomes and 
roots of these plants is dependent chiefly on the shoot for its supply of gases, 
since the heavy, fine-grained mud in which the rhizomes and roots, e. g., of 
Spartina glabra are embedded is practically impenetrable to gases, except 
along burrows of the fiddler crab (Gelastmus pugilator) or those of the muskrat 
(Fiber zbethicus). Of course, except at spring tides, the upper portions of the 
leaves of the higher plants of Spartina glabra will still be exposed at high 
water, and it is possible that, by means of the abundant air-canals, gases may 
be exchanged between all parts of the plant and the outside air. 

For the other species mentioned above, since they grow higher up on the shore, 
the air-supply is not cut off for so considerable a time as for Spartina glabra, 
though this deprivation must still be of some consequence, since such a plant, 
e. g., as Salicormia, will, on the average, be more or less completely submerged 
for from one-fifth to one-third the daylight hours of an average summer day. 

The effect of submergence on the physiological activities of such plants could 
probably best be determined by growing them in a tide-pond the level of which 
could be maintained at a constant level for any time desired. 

For seed plants like Zostera and Ruppia, whose upper limit is not far above 
mean low water, it is probable that the necessary gaseous interchange is accom- 
_ plished during submergence, through the thin-walled epidermal cells. The 
same thing is perhaps largely true for the alge growing between tide-marks. 
Most of these, e. g., the rockweeds, Rhizoclonium, and the Schizophycee, have 
more or less gelatinous cell-walls, which quickly dry on exposure and so form a 
nearly impermeable membrane over the surface. On many days, it is true, only 
the outer exposed branches of Fucus or Ascophyllum and perhaps of other alge 
become really dry on the surface. Hence there may be a considerable gaseous 
interchange occurring even during low tide, a point which can be certainly 
determined only by experiment. 


D. EFFECT OF TIDAL CHANGES ON SALINITY OF SOIL-WATER AT 
HIGHER LEVELS. 

One of the effects of tidal changes may be that of periodically increasing the 
salinity of the soil-water. Near the 8-foot level, e. g., are certain areas where, 
during neap tides, the soil is barely moistened by slowly seeping fresh water, but 
at the fortnightly spring tides the salinity of the soil-water of these areas is 
increased by the salt brought up by the high tides. The effect in these cases is _ 
probably not large. In the case of the fresh-water tributaries of the harbor, 
the change in salt-content with tides of varying height is probably much more 
important. For example, there are growing in the larger streams, between the 
6-foot and 8-foot levels, alge such as Ilea and Hnteromorpha, which may be 


TIDES AND LIGHT SUPPLY 141 


surrounded by pure fresh water continuously for 10 days and then, during 5 or 
6 days of spring tides, be subjected to strongly saline water for from 1 to 2 
hours at each high tide. As was suggested earlier, the effect of this submergence 
is probably not great, except on soils that are comparatively dry in the intervals 
between series of spring tides, since in wet soils the salt water occasionally flood- 
ing them probably does not penetrate far. 

On dry shores, however, there is a strip of soil between the 7.5 and 8.5 foot 
levels where the salt-content is probably increased during each series of neap 
tides. This may be brought about by the constant movement upward of the 
water in the soil by capillarity to levels above that of the high water of the neap 
tides. By the evaporation of the water from the soil the salt will continue to 
accumulate at the levels mentioned until the soil is flushed out by the high 
waters of the spring tides, or by rains. 


E, EFFECT OF TIDAL CHANGES IN EXPOSING PLANTS TO RAIN. 


On the effect of tidal changes in exposing plants to rain there are but few 
observations to record. It is evident that all shore and bottom plants above 
—1 foot may be subjected to a pretty thorough washing with fresh water by any 
heavy rain of the growing season that occurs during low tide. Many of these 
plants, like Spartina and the rockweeds, may be drenched with rain for 6 or 8 
hours at a time and not suffer from it. We have noted above that Fucus and 
Ascophyllum may lie for several hours in pure fresh water at low tide. In the 
case of certain of the red seaweeds, however, such as the Ceramiums on the 
Zostera, and plants of Agardhiella, Chondria, and Polysiphonia, a drenching of 
this sort, especially if followed by exposure to a hot sun, may cause the death of 
the plant. Large portions of the great sheets of Ulva are frequently found dead 
after exposure to such conditions. 

In general, all observations thus far made seem to show that nearly all the 
plants found above mean low water may withstand a more or less protracted 
wetting with fresh water, though only a few like lea, Hnteromorpha intes- 
_ tinalis, and Ectocarpus do, as we have seen in Section III, actually live where 
subjected to this every day. 


F. EFFECT OF TIDAL CHANGES ON THE LIGHT-REACHING PLANTS. 


It is evident that even in clear water the effective solar energy reaching sub- 
merged plants or parts of plants is markedly lessened by each foot of water it 
must pass through. In water of the turbidity of that often found along the 
shores of our harbor it is probable that submergence of a plant in 2 feet or, some- 
times, even in 1 foot of water will practically put a stop to photosynthetic 
activity. In the middle of the harbor the water is usually less turbid. In fact, 
on real quiet days it may be very clear at and near low water. 

From what has just been said it is evident that plants growing below high- 
water mark must do most of their photosynthesis during low tide. A reference 
to plate xxiv will show that since, on half the days of each month, high water 
occurs near the middle of the day (1. e., between 9 a. m. and 3 p. m.), it is evident 
that the most effective sunlight is, on these days, cut off from plants below high- 
water level for a longer or shorter time. This would be most markedly true of 
plants nearer low-water mark, but still true in some degree of all plants below 


142 THE RELATION OF PLANTS TO TIDE-LEVELS 


high-water mark. All these facts taken together show that for a plant growing, 
say, at the 4-foot level (7. ¢., near mean sea-level), the time for the most effective 
photosynthetic work, that is, the total duration per month of emergence during 
brightest daylight (9 a. m. to 3 p. m.) is reduced to about one-half that for a 
plant growing in the open, above high-tide level. In other words, while the 
exposure of an upland plant would be 6 hours in the middle of the day, that for 
plants at mean sea-level will vary from 0.25 to 6 hours per day, averaging 3 
hours per day for the month or season. Since the 4-foot level mentioned is 
about the average level of the photosynthetically active leaves of the lowest 
plants of Spartina glabra we have, in the 3 hours’ exposure mentioned, the 
approximate light minimum endured by this grass. Just what part this re- 
duced lighting may play in determining the lower limit of distribution is 
uncertain. Plants which are left submerged for a longer time than this by 
planting them at mean low water on the harbor bottom die out in one season. 
The effects of the various factors that are changed by this longer submergence 
can only be distinguished and determined by more prolonged experimental work 
than we have yet been able to carry out. 

The above given proportions, of light-reaching plants at different levels, were 
determined from the predicted tide-curves for Willet’s Point, New York, from 
May 1 to October 31, 1911, which are described on page 131 above. This curve 
for Willet’s Point is the closest approximation to that for Cold Spring Harbor 
that can be obtained, the chief difference in the two being the 0.4 foot greater 
height of high water, which would tend to slightly decrease the time of lighting 
of levels from mean sea-level upward. ‘Table D gives the times of exposure per 
day of four selected levels to total daylight, 1. e., from sunrise to sunset, and to 
brightest light, 7. e., from 9 a. m. to 3 p. m., for the month of May 1911, deter- 
mined from the above-mentioned predicted tide-curve. 


TABLE D.—Daily exposure of various tide-levels to daylight. 


Exposure to total daylight. Exposure between 9 a. m. and 8 p. m. 
Level. Hae aayoe ee Average ex- mit, 7 i Average ex- 
posure per |e 52 ee eee ee posure mer 

Minimum. | Maximum. day. Minimum. | Maximum. day. 

Hours. Hours. Hours. Hours. Hours. Hours. 

9 feet (and above).. 13.96 14.93 14.50 6.00 6.00 6.00 
i LOC Se cae scareelets 12.35 14.68 14.02 4.00 6.00 5.54 
Big6i LECT. 56,0: /Beisverauers 6 9.15 t 0.15 6.00 8.00 
O20 TO0tis fetes 0.0 5.60 1.5 0.0 1.25 0.12 


It is interesting to note here that the 0.0-foot level may not be exposed at all 
to daylight for 8 days at a time, and not be exposed at all between 9 a. m. and 
3 p. m. for 25 days out of the month. In this connection, however, we must 
recall again the often great clearness of the water in the center of the harbor at 
low tide, which allows plants at and below this level to get rather intense light © 
at low water, even though submerged by a foot or more of water. Since in the 
case of extreme spring tides high water always occurs in the middle of the day, 
the 9-foot level, if submerged at all, is covered between 9 a. m. and 3 p. m., the 
hours of brightest daylight. 


SALINITY OF WATER 143 


It is evident that the habitat of the lower plants of Spartina glabra really 
resembles that of shade plants, so far as light supply and moisture conditions 
are concerned. Though they do not show very striking differences in structure 
when compared with plants of the same species growing near its upper limit, 
some differences are discoverable. For example, the plants at the 2-foot level 
have weaker stalks, thinner and narrower leaves, thinner cuticle and _ less- 
developed photosynthetic tissue than plants at the 6-foot level. Of course, many 
plants growing at and below mean low-water level are decidedly like shade plants 
in many respects, as has been suggested by Warming (1909, p. 150). For 
example, Zostera and Ruppia have the attenuated form characteristic of plants 
etiolated by shade. In the case of the alge Ulva, Enteromorpha, Cladophora, 
etc., found near low-water mark the structure is not markedly different, so far 
as was noted, from that of the same species at the highest levels these attain, 
except that the latter are smaller (perhaps we may say more stunted in growth). 
This is probably due to the fact that plants on piles and wharves at higher levels 
are more likely to be torn with the fall of the tide than are plants that lie on 
the bottom. A careful statistical study of the size of plants, of their cells, or the 
thickness of their cell-walls, might show constant differences in plants at 
different levels not hitherto detected. On the other hand, plants at the 7-foot 
level may get the maximum exposure of 6 hours per day to brightest daylight 
on 24 days of the month and lose an hour and a half or more of this light on 
only 4 days per month. Thus plants like Spartina patens, Distichlis, Salicormia, 
and Sueda, growing between 6.5 and 7.5 feet, are probably not much affected 
» by the relatively small proportion of total daylight lost by submergence. 

The general conclusion must be, then, that the shortened light supply of 
plants subject to daily submergence must affect their physiology, their structure, 
and hence their possible vertical range, in a very considerable degree, especially 
if they grow at or below mean sea-level. The exact effect of different exposures 
to light on different species of these plants has yet to be determined experi- 
mentally. 

In summary of the various effects of tidal changes on plants, we find that these 
are of most general importance in affecting, first, the amount of transpiration ; 
second, the time available for gaseous interchange between the shoots and the air ; 
and, finally in limiting the light-supply and hence the effective photospnthetic 
activity of littoral plants. Of secondary and only occasional importance are 
the effects on concentration of the soil-water at high levels, and the exposure of 
plants near mean low water to rains during low tides. 


4. THE SALINITY OF THE WATER OF THE HARBOR. 


The normal specific gravity of the water near the surface of the harbor, at high 
water, was found to be 1.022 (at 15° C.). The salinity, and so the specific 
gravity, varies somewhat with the state of the tide, and may become much lower 
than 1.022 at low water. This lowering of the specific gravity is evidently 
due to the large admixture of fresh water from tributary streams and springs. 
The inflow of this fresh water remains constant, except that from springs 
between tide-marks, while the volume of water in the harbor with which this is 
mixed decreases very rapidly with the falling of the tide. The cubic contents of 
the harbor at high water is about 42,000,000 cubic feet, while at mean low water 

10 


( TABLE E.—Vertical distri 
COMPOSITION OF 








Tide Levels. 


12 feet. 


Thallophytes. 





Vegetational Belts. Supra-Littoral Beach. Supra-Littoral Mar 





Species. Range.* Species. R 





11 feet. 


10 feet. 


9 feet. 


8 feet. 











Cladonia sp. | 9 to 12 s Lyngbya sp. 8 


s Nostoc sp. 8.£ 





| 
| Supra-Littoral Belt. 
| 8 to 12 feet. 
(Storm Beach and Supra- 
Littoral Marsh.) 











7 feet. 


6.5 feet. 





¢c Rhizoclonium tortuosum.........ee.ee0. ae coments 
S$. Calothrix,(4:sp3) <2\0cce sanescceure alviare lato cualeve ofalere ae 
8 Microcoleus cht onoplastes rain sere UiAaisis Se aera s . 
CO  ViAUCHETIR AED caictsls ow inw cc chats cy mee orelatereictarels ainiatetsiote 
e Enteromorpha intestinalis Esinieataperateratarciaioiate aeveictiers 
8 Lyngbya (8 sp.)..... aisiaice shefaisie eteuatae einai 
@ Flea. fulveseens..... 0.56 2ss0008 Sipiasite mesiterers tee 
c Monostroma latissimum.........0...-2000. Rh we'eee 
$ Spirulina tenuissima sac css. sceeen eee ee 


Upper Littoral Belt. 
6.5 to 8 feet. 
(On all shores.) 


CONrNOCUr SY 
Sion 





6 feet. 


5 feet. 


4 feet. 





3 feet. 


2 feet. 


1.5 feet. 


1 foot. 


0 foot=M. L.W. 


2 foot. 


—2 feet. 





—83 feet. 





* The two numbers given under ‘‘range’’ indicate the levels (above mean low water) between which the 




















on 


e Rhizoclonium tortuosum..............cceseeeeees 
¢ Rhizoclonium riparium...........ccecsseessseses 
f Bostrychia rivularigs....ctecces cee eee None 
cM lothrix aeca., Acdses se os bis Saeiste se sipnte comnts 
S$ Anahena tortiloge 1.4.54. 0s assur easeneckas tore 
$s Lyngbya MOSUUALUL cies 'cc cease Set eeaicke oe eee eee 
s Microcoleus chthonoplastes.... gia tetas Slgisvelecebornn ents 
p Ralfsia clavata........... ee Sialetess niciatetckensratatataierors arcs 
r Hildenbrandia prototypus..............s00. Abt 
ce Enteromorpha intestinalis..............- a aelcicisinte 
euMonostroma. latissimum......,.200-cene ves eee 
e Ilea fulvescens.......... oa ciate crefavele eis sterss civ ate. ere esis 
O Vauch6ria :p; «shechande cco sansorreeacee ani n ees ‘ 
ce Cladophora expansa...... m siviole ais Sieve rersielsreiclelayenyeters = 
p Pylaiella littoralis robustus....... b sgieiddeseitaies ¢ ‘ 
¢ Delesseria leprivril.? coco eee use lee tee eee 
SSRIVAIATIA BELA cicewes vets acces aoe eee ee 
© Porphyra laciniata... cece ter ee eee eee Abe 





DUH RAED OM ORR RWWA Om 


Mid-littoral Belt. 
1.5 to 6.5 feet. 
Mid-littoral Marsh and 
Mid-littoral Rockweed 
Association. 


Gin 


I 


wr 

















cr Ulva lactucaslatissining «sts... ess vs. occe cesses —5 
¢ Knteromorpha clathratac.......0.esoeeroueeerrente —1 
ce, Hnteromorpha intestinalis..2. .\.;.o.scesseuen aie ee 2 0 
p Ascophyllum nodosum,..sc.c...cet cheese ses de nel ~*T 
pi Fucts vesiculosus.) 2c cad. ecto oe ee arrays Se 0 
r Porphyra paeeance siesa'e¢ oxb.0l'e shoves > leaner eet meee etetata oo : 
: rf Oeramium rubrum. adse- sear alee eee es = _ 
iti Hag os r Ceramium strictum.......ceccasccscserracessencs —2 
(Lower Littoral and Sub- p Pylaiella littoralis robustus .............s0e20e0: —1.5 
littoral Belts.) r Ohondrus Crispus... oc oc save dacs ccetentn e's eet ooae 
; | p Ectocarpus confervoides. .....6c.sncecccccccccvecs 0 Fl 
r Hildeabrandia prototypus...........s+06 Misteisie leis —1 | 
y Agardhiella tenera erates. ste retids. ccc sc cces —1 
S$ Spirulina: tentisslmaaioec-remoc eins skis are ea os ¢ 0 
rf Delesseria leprieuriist...-..csecccss ccc ces cee cess =1 
Melosira nummiloides.\ iesimisinweciss ras sawiciemacres : —1 
Navicula grevill@iti... cose fecesenecers tect teats —1I 


p Ascophyllum nodosum, ss sess sccccdessadisscssvece 
p Fueus vesiculosus: cect ccke toceep es eee tear ais oe | 
p Fucus vesiculosus spiralis................ Beara eis 








| 
1 








The small letter before the name of each species shows to the eye, in glancing down the column, the phy 
8 = Schizophycex, d = Dicotyledonez, and m = Monocotyledonex. 


‘ion of more common plants. 


































































IGETATIONAL BELTS. 
| Cormophytes. 
| 
| Supra-Littoral Beach of Spit. Supra-Littoral Marsh. 
————. | eee eee eee 
e.* | Species. Range.* | Species. Range.* 
| 
|| m Ammophila arenaria....... 8.3 to 12 m Scirpus americanus........ 6.5 to 12 
d Cakile edentula............ 8.5 11.5 Aspidium thelypteris.......| 8.5 12 
d Solidago sempervirens..... 8 11.5 m Juncus Gerardi............. 7.3 8.8 
‘ d Lathyrus maritimus....... 10 11 i aed DALens. aise sees: 6.5 8.7 
? d Euphorbia polygonifolia... 8:5 12 m Eleocharis olivacea........! 8.3 12 
d@ Salsola kali....... ae 8.5 12 | m Scirpus robustus........... 6.8 8.7 
? d Xanthium echinatum....... 10 a d Solidago sempervirens..... 6.5 12 
d@d Aster tenuifolius........... 9 11 & Eva GOFATIA «LO. S. eee tents 425 8.5 
d Atriplex arenaria.......... 6.5 8.7 d Aster subulatus............ 7.3 9 
d Rhus toxicodendron........ 9 12 d Hibiscus moscheutos....... 8 12 
US UAT IETS EY oy eee Ace eee 11 12 d Gerardia maritima......... 8 8.7 
d Polygonum scandens....... 9 12 || m Distichlis spicata.......... 6.5 8.5 
d Ailanthus glandulosa....... 9 12 d Lysimachia terrestris...... 9 ? 
d Verbascum thapsus......... 9 12 d@ Asclepias incarnata pulch.. 8.3 12 
m Agropyron repens.......... 8.8 12 m Agropyron repens.......... 8.7 12 
ad Galium claytoni............ 8 12 Solaginella apus........... 9 12 
d Oenothera biennis.......... 11 12 Pallavicinia lyellii........ 9 12 
d Robinia Pseudo-Acacia..... 9 12 
Geax anes AIL, ase cde de 18 12 
d Polygonella articulata..... 10 12 
m Spartina patens.......... aie 6.5 to 8.7 d Atriplex patula hastata.... Gito 8-5 
a@ Sueda maritima............ 6.5 8 d Limonium carolinianum.... 7.3 8.3 
5 d Salicornia europxa......... 6.5 7.5 d Plantago decipiens......... 6.3 8.3 
m Juncus Gerardi............. URE 8.8 MSIL PUA NANUSE sos cb eace ek. 6.3 8 
k (is m Scirpus americanus....... - 6.5 12 m Triglochin maritima....... 6.3 7.5 
7.5 m Scirpus robustus........... 6.8 8.7 m Typha angustifolia......... 7.8 12 
pas m Distichlis spicata.......... 6.5 8.5 
Ce @ Salicornia ambigua........ 6 0 
i _|| d@ Spergularia marina........ f 8 
7 | 
7.25 m Spartina glabra alterniflora.................68. Asieideveisiatalarele inlays oh eG as pate cue eet: eon tow Gro 
6 
8 
ie | d@ Lilzopsis lineata............ ey stavetgialsisiala sal ofNales alaivintre ral citis aie aie’ ap s:ciois alsienic s) sléisiainie’seis's 5.5 6.5 
6.5 
7 
7 
7.5 
| ea 
a 
7.25 
ao... 
7.5 
7 
7 
4.5 
5 
6 
4 
25 | m Zostera Marina,.......ces-06 TOOL RDO Re ACOCS CONDE OCOCCCBOHOL ONE & aoa e OR ORenCE ie <3 tO} 1.5 
mBuppia Maritimiars. vs .cccdsss.vetcce ene nVsiel Selatan Ricinie ele tics ices aiainieisisin er neetecietiia cs era 0 1 





Rear e e e  e 
usually grows. The species are given in each belt in the order of prevalence. 


etic relationship of the forms of each belt. Thus: c= Chlorophycee, p = Phxophycex, r = Rhodophycex, 


146 THE RELATION OF PLANTS TO TIDE-LEVELS 


this is reduced to about 2,250,000 cubic feet, and at a low water of —1-foot, 
during spring tides, the volume may be only 700,000 cubic feet, or one-sixtieth 
of that at high water. 

There is no adequate evidence that these variations in salinity are of con- 
sequence to the plants found established in the harbor. The low salinity at low 
water, however, may well be an important factor in preventing other red alge, 
now occurring in the Outer Harbor, from getting a foothold in the Inner Harbor. 

Of far more importance are the relatively rapid changes from water of a 
specific gravity of 1.019 to absolutely fresh water, and the reverse, to which 
plants growing between tide-lines in the fresh-water tributaries are subjected 
twice each day. We have already spoken of the algew Hnteromorpha intestinahs, 
Ilea, and Monostroma as occurring in or near fresh-water tributaries, where at 
high water they are surrounded by salt water, but, with the fall of the tide, are 
left with fresh water running over them, often for 8 or 10 hours continuously. 
The transition from one extreme to the other may, in the case of the small 
rivulets, occur very suddenly, probably in the course of a very few minutes. 
This is true because where there is but a small flow from a rivulet it may cause 
little mingling of the fresh and salt water about the alge until the water has 
fallen almost to their level. Up to this time the fresh water, being lighter, simply 
spreads out on top of the salt water and leaves the alge, which may be but an 
inch or two below, surrounded by salt water. Even in the case of larger streams 
such as that entering the harbor from the ponds of the New York State Fish 
Hatchery at 600 south by 720 east, Miss Streeter found that the water at the 
bottom, surrounding the alge, may change from a specific gravity of 1.014 to 
one of 1.000 in an hour’s time, with a fall of but 1 foot in the tide. 

From a careful study of the floras of the between-tides portions of fresh-water 
tributaries, all about the harbor, it is evident that the rapid changes in salinity 
of the water must prevent many plants found elsewhere from growing in these 
‘areas. On the other hand, the ability of the alge mentioned to withstand these 
conditions make these areas places of refuge for these alge, where they are free 
from the competition of other species; Ilea, e. g., for example, covers many 
square meters of the pebbly bottom of the Creek, between 200 and 500 south, 
practically to the exclusion of other species, except the inconspicuous diatoms. 
It must also be recalled that these rivulets have another advantage, perhaps the 
principal one, in that they form habitats where these more delicate alge are not 
subject to desiccation during low tide, as they would be elsewhere at the same 
levels. 

The salinity of the soil-water on various portions of beach and marsh, both at 
the same and at different levels, is undoubtedly a factor of very great importance 
in determining the distribution of plants. Reference has been made in the body 
of the paper to the fact that Lilea subulata, Scirpus americanus, and S. robustus 
are found chiefly in soils more or less saturated with fresh water, and to the 
fact that Iris versicolor, and probably Hibiscus moscheutos, push down to their 
lowest levels in spots where the soil, though below high-water mark, is saturated 
by running or seeping fresh water. A series of quantitative determinations of 
the salinity of the soil-water in various of these habitats has been initiated, but 
determinations are not yet numerous or complete enough to allow of detailed 
discussion. The method being used is like that used by Harshberger (1909, 


TEMPERATURE OF WATER 147 


1912) in the study of the New Jersey marshes. It is hoped that the results of 
these determinations may be presented in a later paper by the junior author of 
this one. 


5. THE TEMPERATURE OF THE WATER. 


On the subject of the temperature of the water also we have no quantitative 
results to present. A few measurements of the temperature at the bottom and 
at the surface of the middle of the Inner Harbor at high tide (of 7.5 feet) were 
taken in July 1909, which showed a difference of but 1° or 1.5° C. In Miss 
Streeter’s records made in July, the temperature of the stream at 600 south by 
720 east was found to vary from 9° C. at low tide to 18° C. at high water. Itis 
evident of course, that plants like Zostera, Ruppia, Ulva, etc., which lie on the 
black, heat-absorbing mud in the sun at low water, must often be heated to 30° 
or 35° C. or higher, in the summer. When, on the contrary, these plants are 
exposed at night, their temperature must fall at least to 10° C. or lower, since 
the air temperature may go down to 8° or lower during the growing season. 

Just what part the seasonal change of water-temperatures plays directly, in 
determining the seasonal development of the alge of the bottom, can not yet 
be stated. It is a well-known fact that the algal flora of a given locality varies 
markedly from winter to summer. In Section III of this paper it has been 
pointed out that not only are certain of the characteristic summer forms wanting 
in April and December, but in the former month, at least, Ulva, one species of 
Ectocarpus, and Porphyra were far more abundant in the Inlet than they have 
ever been in the summer. The rockweeds all about the harbor, which in summer 
bear practically no epiphytes, were found densely coated with filaments of 
Ulothriaz flacca. In just how far the low temperatures of winter are directly 
responsible for the abundance of these alge in winter, or whether they may be 
indirectly responsible by affecting the evaporation, has not yet been ascertained. 
Possibly, as Warming suggests (1909, p. 151), experimental physiological study 
may show that the larger proportion of dissolved O and CO, held by the water 
when cold offers the real explanation of the greater abundance of certain species 
in winter. The whole subject of the winter activities of marine plants is 
greatly in need of continuous study, such as has now become possible, with our 
many well-equipped marine laboratories. 


V. SUMMARY AND CONCLUSIONS. 


The Inner Harbor of Cold Spring Harbor has an area of 110 acres at high 
water. At low tide it has an area of 45 acres, with a maximum depth of 7 feet 
over an area only 100 feet in diameter. The mean range of tides is 7.75 feet. 

By the aid of two series of perpendicular range-lines, marked with stakes, 
the positions of tide-lines, or of plants on the shore or in the harbor, could be 
accurately determined and recorded. A tide-curve was constructed from read- 
ings made on a tide-stake, and checked by one made later by a self-recording 
tide-gage. From this tide-curve the times of submergence and exposure of 
shore-levels, and thus of plants, were determined. 

The chief vegetational zones or belts distinguished, with their upper and 
lower tidal limits, are the following: (1) The plankton, of Diatomacez and Peri- 
dinew. (2) The bottom vegetation (—5 to +1.5 feet), including the “ enhalid 
formation ” of Ulva, Enteromorpha, Zostera, and Ruppia; the “ lithophilous 
benthos ” of Enteromorpha, Ulva, Fucus, Pylaiella, Chondrus, Porphyra, etc., 
attached to stones and shells, and the epiphytic alge on Zostera and Ulva, 
chiefly diatoms, Enteromorpha and Ceramium. (3) The mid-littoral belt (1.5 
to 6.5 feet). This is the most clearly limited belt about the harbor. It in- 
cludes a Spartina glabra association on sloping shores and a rockweed associa- 
tion, of Fucus, Ascophyllum, and Bostrychia, on the wharves. (4) The upper 
littoral belt ( 6.5 to 8 feet), which has a more varied vegetation, including asso- 
ciations of felted filamentous alge, of Spartina patens, of Salicornia, of Sueda, 
and of Scirpus, each either pure or mixed with members of one or more of the 
other associations mentioned, or with more or less scattered individuals of Scir- 
pus, Distichlis, Atriplex, Limoniwm, or Spergularta. (5) The supra-littoral 
belt (8 to 12 feet). ‘This is less clearly defined and more varied in make-up 
than the other belts. It includes associations composed of Ammophila, Solidago, 
Salsola, Cakile, and Lathyrus, of Scwrpus americanus and 8S. robustus, of 
Aspidvum thelypteris, and also includes more scattered and mixed groups of 
Asclepias, Aster, Baccharis, and Hibiscus, besides many upland plants. 

The external environmental factors which influence the distribution of plants 
in this harbor are: substratum, water-currents, changes in water-level with the 
tides, salinity, and temperature of the water. 

The substrata, aside from living plants, vary from fine silt, humus, or peat, 
to sand, gravel, rocks, and logs. The plant-covering at any level differs with 
the type of substratum, depending largely on the drainage possible. The soft, 
undrained mud of the very bottom of the harbor bears only Zostera, Ruppia, and 
anchored plants of Ulva and Enteromorpha. Other plants of the bottom, all of . 
them alge, require a firm substratum, as stone, a shell, or another plant, for 
attachment. ‘T’he physical character of the soil greatly affects the rate of 
drainage of salt water from shore between the tide-lines and of fresh water 
from the upper levels, and thus determines the type of vegetation growing on 
them. For example, where the soil of the Spit above the 6-foot level is gravelly 


148 


SUMMARY AND CONCLUSIONS 149 


and well-drained, Spartina glabra grows but little above this and is succeeded 
by Salicornia and Sueda, while on the peaty soil of flatter parts of the shore 
S. glabra may extend up to the 7.5-foot level and there be succeeded by Spartina 
patens or Distichlis. If fresh water is present in the fine soil of the upper levels, 
Spartina glabra is succeeded by Scirpus americanus and sometimes mingled 
with it up to the 8-foot level. On the Marsh the character of the vegetation of 
the surface is correlated with the local thickness of the peat above the underlying 
gravel. 

The effects of water-currents on the distribution of plants are exercised by the 
dissemination of spores and seeds and by the breaking off and transportation of 
the shoots of Zostera, and of alge like Ulva, Enteromorpha, Fucus, etc., which 
persist and grow in their new lodging-places. In other cases water-currents, by 
mechanically injuring the plants or by determining the character of the sub- 
stratum, may favor or retard the further extension of a species. On the other 
hand, the rapid movement of the water is an evident advantage to some species, 
perhaps by increasing the interchange of material between the plant and the 
surrounding water, and possibly also by injuring competitors. Thus Zostera, 
Cladophora, Pylaella, Chondrus, Polysiphonia, Porphyra, etc., are most abun- 
dant in or beside the rapid tidal current of the Inlet. Jlea, Monostroma, and 
Pylatella likewise are abundant only in the rapidly flowing Creek entering the 
south end of the harbor. 

A careful study of the vertical distribution of the littoral plants about this 
harbor shows that this depends primarily and very definitely on the relative time 
of their submergence and emergence with the rise and fall of the tide. Moreover, 
the vertical range of littoral species is strictly, sometimes very narrowly, limited. 
There are no species here, except two or three alge, that are distributed 
“between tide-marks” (1. e., from low water up to high water), as is so often 
reported. The nearest approach to this range found for any seed plant is that 
of Spartina glabra, whose vertical range of 5 feet (from 1.5 to 6.5 feet above 
mean low water) lies midway between the limits of the average (8-foot) 
tide. The range of this salt reed-grass covers but five-eighths of the mean tide- 
range and only half the range of many spring tides of the growing season (10 
to 11 feet). This Spartina never gets below 1.5 feet and only in exceptionally 
moist and shaded areas does it grow at any appreciable distance above 6.5 feet. 
The alga Fucus ranges from just below mean low water up to 7.25 feet and 
Enteromorpha intestinalis has a similar range on shores where fresh-water 
rivulets flow in over the upper beach. The other seed plants of the shore range 
down to but 1.5 or 2 feet below mean high-water level (7.75 feet), with the 
exception of Lilgopsis, which is found between 5 and 6.5 feet. Zostera and 
Ruppia range upward for only 1 or 1.5 feet above mean low water. 

The essential feature, for our purpose, of the tidal oscillation of water-level 
is the relative times of submergence and exposure experienced by the various 
shore-plants. For the sake of comparison this relation is most significantly 
expressed in a fraction for the upper limit and one for the lower limit of distri- 
bution of each species (p. 135). The influence of this change in water-level 
on the plant is effected through differences, at different levels, in evaporation 
rate ; in aeration; in salinity of soil-water at higher levels; in exposure to rain 
and in light supply. It seems evident, for example, that Spartina glabra 


150 THE RELATION OF PLANTS TO TIDE-LEVELS 


and the rockweeds do not grow at levels above 6.5 feet, because they can not 
endure a greater evaporation than that experienced here. Zostera and many 
alge for the same reason are confined to levels below mean low water, except 
where washed by tidal streams during low tide. It seems probable also that the 
too brilliant light or the exposure to rains during low tide prevents certain algee 
from growing above mean low water. On the other hand, certain plants are 
stopped in their spread downward because they can not endure the longer sub- 
mergence, with the lessened aeration and light supply, at lower levels. Spartina 
glabra, for example, as has been shown experimentally, is undble to persist 
more than a few months at levels even slightly below 1.5 feet. The rockweeds 
also seem unable to persist below the level just mentioned in the usually quiet 
and turbid water of the Inner Harbor. In the clearer, rapidly moving water of 
the Inlet, however, and especially in that of the Outer Harbor and Long Island 
Sound, Fucus grows a foot or more below mean low water. 

The degree of salinity clearly determines the horizontal distribution of many 
plants in this harbor. For example, one series of alge, chiefly Chlorophycee, 
occur only in the less saline south end of the harbor, where they are flooded with 
fresh water for from 2 to 10 hours each tide. On the other hand, the majority of 
the Floridee found here grow in the channel to the Outer Harbor, where the 
water is most saline. 

In the list of plants of the harbor (pp. 151 to 161), there are indicated for 
each species the physical characteristics of the habitat which are believed to be 
concerned with its distribution. In but relatively few instances has the connec- 
tion between the distribution and external conditions been experimentally shown. 
Though the attempt has been made in the body of this paper to suggest the 
external factors determining the distribution of each common species, this must 
be regarded as a suggestion of the elements entering into the problem rather 
than as a statement of its definite solution. 

It is believed that the determination of the relative time of submergence and 
exposure of a plant at its upper and its lower limit in this harbor, where the 
range of tide is about 8 feet, will make it possible to predict the vertical range 
of the same species in any other region, if the range of the tide is known. 
That is, the vertical range of a littoral plant is exactly proportional to the range 
of the tide. 

In this study chief attention is devoted to determining and recording as 
accurately as possible the present distribution of the plants of this harbor in 
relation to tide-levels, salinity, and soils. Little has been said of the succession 
in time of the formations occurring at different levels on the shore. It is 
believed that this historical aspect of the problem can be solved more satis- 
factorily by the comparison of the vegetation that will exist here some years 
hence with that which is here recorded. 


VI. LIST OF VASCULAR PLANTS OF THE BOTTOM AND SHORE, 
WITH VERTICAL RANGE AND THE PHYSICAL CHAR- 
ACTERISTICS OF THE HABITAT OF EACH. 


EXPLANATION OF TABLE F. 


The data included in Table F are those listed immediately below, and they 
are indicated for each species found below the 12-foot level as far as known. 
Each characteristic of the plant or its environment is indicated in the proper 
column by a word or phrase, or, for the sake of brevity, by the symbol indicated 
in this list of data. 

The 12 data noted for each species in Table F are arranged, in a horizontal 
line, in the following order: 


if Symbol: This is used to indicate the species on charts and plates. 
II. Name of the species: The nomenclature in the case of ferns and seed plants 
is that of Gray’s New Manual of Botany, seventh edition. 

III. Habitat and persistence of the species: 

1. Annual herb: an. 

2. Biennial herb: bi. 

3. Perennial herb: per. 

4. Shrub or woody vine: sb. 

5. Tree: tr. 

TV. Density of stand or frequency of individuals of the species: A dash separating 
two symbols indicates that the density varies from the first to the 
second type. 

1. Pure stand: pure. This is used only where a species may cover from 
several square decimeters to, in other cases (e. g., of larger species), 
many square meters, with dozens, scores, or hundreds of individuals. 

2. Mixed: preponderatingly, or nearly equally, with another species. This 
will be indicated by the use of the symbol for the second species 
thus: + Sp. means that the species in question has Spartina patens 
mixed with it. 

3. Seattered: among a second species and less abundantly than it; e. g., 
Sp. + indicates that the species is mingled with Spartina patens 
and is outnumbered by the latter. 

4. Grouped or clumped: gpd. 

5. Seattered, occasional, or isolated: oc. 

V. Substratum: Of the 9 substrata listed the last 4 will be used only in the list 
of alge. 

1. Mud: md. This is soft, saturated soil, usually sparsely covered. 

2. Humus: hu. Used for dry or moist humus-containing soils, except the 
peaty soil on the Marsh. It includes the very sandy humus of the 
top of the Spit. 

3. Peat: pt. This includes soils, wet or moist, chiefly of organic origin, 
and bound together by dead and living roots and rhizomes. 

4. Sand: sd. This may be dry, as at high levels on the Spit, or nearly 

saturated when between tide-marks. 

. Gravel: gv. Chiefly near high-water level. 

Rock: rk. This includes larger pebbles, the stones of the wharves, and 

boulders of the bottom or shore. 

. Shells: sh. The shells of living and dead lamelli branch and gastero- 

pods. 

. Wood: wd. Stakes, the logs of wharves, and sunken trunks or stakes 

on the bottom. 

. Living substratum: Chiefly Mytilus edulis among animals and Zostera 
and Spartina glabra among plants. Less commonly Ulva and the 
stouter red algsze may serve as substrata for certain diatoms and blue- 
green alge. Thus, e. g., ep./Z. means epiphytic on Zostera. 


151 


ie) co “a 2 Ol 


152 THE RELATION OF PLANTS TO TIDE-LEVELS 


VI. Salinity of the soil water during the growing season: It may be more saline at 
levels above 8 feet in winter, due to storms, or, even in the growing 
season, the salinity may temporarily become somewhat greater 
near the high-water mark from the concentration due to evapo- 
ration. It may again be less saline at these upper levels after rains. 

1. Salt: sa. By this is meant water of the density of that usually found 
at the surface of the harbor at high tide, which has a specific gravity 


of 1.019. 
2. Brackish: br. Distinctly less dense than the above. 
3. Fresh: fr. 
VII. Light demands: That is, the light conditions under which the species usually 
grows. 


1. Sun plants: su. 
2. Shade plants: sd. 

VIII. Upper limit of vertical distribution: The average upper limit of distribution 
of the species is given in feet above mean low water (indicated by 
the plus sign) or below mean low water (indicated by the minus 
sign). Where 12 feet + is used in this column it indicates that the 
plant may grow at this level, which is the highest level reached by 
winter tides, and at any level above this. That is, the plant is not 
confined to sea-coasts. In all other cases the upper limit given is 
the highest level at which the plant has been found about this 
harbor. Where but few individuals have been seen, and so the 
possible vertical range could not be determined with certainty, the 
one level at which it was found is indicated in this column and the 
column for the lower limit is left vacant. 

IX. Lower limit of vertical distribution: The average recorded lower limit of dis- 
tribution is given in feet, above or below mean low-water level for 
the soil upon which the plant grows at this limit. The extremes of 
distribution are given in Section III. The plus and minus signs 
are used as in column VIII to indicate levels above and below. 

X. Emergence or exposure: This is given, in the average number of hours per 
lunar day, for the soil which bears the plants at the upper limit of 
the species. It thus indicates the greatest average exposure endured 
by any plants of the species, aside from the few exceptional indi- 
viduals that may occur at slightly higher levels in habitats where 
the shade or moisture conditions are especially favorable. The data 
for emergence are taken from Table A (p. 135). Additional infor- 
mation concerning the occasional exposure of low levels and the 
duration of continuous exposure of higher levels may be obtained 
from Tables B and C (p. 136). The exposures during the hours of 
daylight may be seen from Table D, on page 142. Of course, the 
exposure of the soil on which a plant is growing indicates merely 
the exposure of the shoot above the soil. The subterranean por- 
tions are still immersed in a soil that may be practically satu- 
rated with salt water, e. g., Spartina glabra, or with fresh water, 
e. g., Sagittaria latifolia. 

XI. Submergence: This is given for the soil on which the plant grows at the usual 
lower limit of distribution of the species, as indicated in column IX 
of Table F. The submergence given thus indicates in hours per 
lunar day of 24.9 hours, the average submergence endured by the 
lowest plants of the species in question during the growing season. 
The duration of submergence here given is taken from Table A 
(p. 185) and is calculated in the manner mentioned in the explana- 
tion of that table. The number of submergences per month or per 
growing season for plants near the high-water level, or the duration 
of continuous submergence of plants near mean low water, can be 
learned from Table B and Table C (p. 136). The occasional sub- 
mergence of levels between 9 feet and 10 feet by storm tides is sug- 
gested in the cases of plants growing at these levels. Only winter — 
storm tides ever cover levels much above 10 feet. 

XII. Ratio of emergence to submergence: This is given for plants at the lower 
limit of vertical distribution of the species and at the upper limit. 
The two figures thus indicate the range in conditions, so far as the 
latter are affected by the tides, under which each species shows 
itself capable of growing here at Cold Spring Harbor. It is probable 
that if one had the tide-curve for a habitat with tides of greater 
magnitude like Nova Scotia or one with tides of lesser magnitude, 
like Virginia, he could predict the vertical range of any species 
common to one of these localities and to Cold Spring Harbor. 


153 


LIST OF VASCULAR PLANTS 





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THE RELATION OF PLANTS TO TIDE-LEVELS 


156 














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VII. LIST OF THALLOPHYTES OCCURRING BELOW THE 
10-FOOT LEVEL. 


EXPLANATION OF TABLE G. 


In addition to the algx, 2 bacteria, 2 lichens, and 2 bryophytes have been 
recorded. All of these are given at the end of this list of alge. The names 
used for green alge are those of F. S. Collins (Chlorophycee of North America). 
pa used for the Pheophycee and Rhodophycee are chiefly from Farlow’s 

“ Marine Alge of New England.” 

While the number of lower plants growing on the east and et shores, 
between the 9-foot and 12-foot levels, may be considerable, they are, as far as 
noted, such as occur far above sea-level. Therefore, aside from the alge of the 
fresh-water rivulets, they are not here listed. The lichens and mosses of the 
Spit, even from the top, are included, because this is such an essentially littoral 
habitat. 

Symbols are given for part of the forms only in this table, these being the ones 
whose distribution is indicated by means of these symbols on plates rx and x. 
In cases where the distribution was not determined separately for each of the 
several species of a genus, the same symbol has been used on the maps to indicate 
any species of the genus found in a given locality. This collective use of a 
symbol is indicated in Table G by a bracket embracing the various species 
included under it. 

The characters of the plants and their environments which are noted in 
Table G are those given for the vascular plants, with the exception of “ light 
demands.” ‘These are omitted because few definite and significant data are 
available. Of course, many of the alge of the bottom and wharves, growing 
between tide-marks, are in a sense shade plants, protected by submergence, as 
was suggested in regard to Zostera and Ruppia in Section V. Other alge 
growing between the 4-foot and %-foot levels among the stalks of Spartina 
glabra, S. patens, and the Salicornias are also shaded by these larger plants. 
Other species still, like those of Calothrix and Lyngbya, grow in full sunlight 
on the open beach, or on the wharves even near the 8-foot level. These are 
subjected to rather intense light and desiccation, and during neap tides may 
not be touched by the water for several days together. Finally, the alge of the 
Inlet below —1.5 feet and those of fresh-water streams are never exposed to 
full sunlight. 

Certain alge, e. g., Ulva, Agardhiella, Fucus vesiculosus spiralis, etc., may 
persist for weeks or months unattached to the substratum. Where a species may 
occur free in this manner this fact is indicated in the column for substratum by 
the symbol “ fr.” 

Since none of the alge penetrate far into the substratum, the salinity of the 
soil-water is of little consequence to them. The salinity of water surrounding 
the shoot is the thing of importance, and it is this, therefore, that is given in 
the list. This salinity may, as is indicated, differ greatly at different stages of 
the tide. This is especially true for plants living near fresh-water streams. But 


157 


THE RELATION OF PLANTS TO TIDE-LEVELS 


158 


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DIATOMACE 161 


any alga growing between tide-marks may be washed by fresh water during 
heavy rains at low tide. 

The stand of any given alga may be pure over several square centimeters, a 
few decimeters, or, in some species, over some square meters. The vast majority 
of species, however, are mingled more or less abundantly with others, or occur 
sparsely, or even rarely as individuals, attached or free, often with no others of 
their kind within a distance of many meters. The latter is often true, e. g., of 
Agardhiella, Gracilaria, Porphyra, etc. Where but one or a few collections of 
a species have been made, and all at one level, this level is given under “ upper 
limit.” 

DIATOMACE. 

Besides the diatoms mentioned in Table G, a number of other species were 
identified by Dr. Albert Mann, in collections made on November 30, 1912, from 
the 3-foot level on two stakes in the middle of the harbor and from shells in the 
Inlet near the 1-foot level. They were not sought elsewhere and therefore their 
general distribution can not be given, as their colonies are not large enough to 
be conspicuous among the other alge of their habitats. The following include 
all the diatoms thus far identified from the Inner Harbor: 


Achnanthes brevipes Ag. Navicula alternans Schum. 
hauckii Grun. grevillei (Ag.) Cleve. 
longipes Ag. Kennedyi W. S. 
Actinoptychus splendens (Shad.) lyra Ebr. 
Ralfs. marina Ralfs. 
Amphora eulensteinii Grun. smithii Breb. 
Biddulphia aurita ,Lyngb.) Bred. Nitzschia acuminata W. S. Grun. 
Cocconeis scutellum Ehrb. longissima (Breb.) Ralfs. 
Coscinodiscus asteromphalus Ehrb. panduriformis (Greg.) 
decrescens Grun. Grun. 
excentricus Ehrb. paradoxa (Gmel.) Grun. 
radiatus Ehrb. sigma W. S. 
Cyclotella striata (Kg.) Grun. Pleurosigma angulatum W. S. 
Fragillaria brevistriata Grun. balticum W. S. 
Fragillaria sp. distortum W. S. 
Gomphonema curvatum Kg. intermedium W. S. 
Grammatophora marina Kg. Podosira subtilis (Bail) Mann. 
Licmophora tincta (Ag.) Grun. Synedra affinis. 


Lithodesmium undulatum Ehrb. 
Melosira borrei Grev. 
nummuloides (Bory.) Ag. 


VII. LITERATURE REFERRED TO. 


BAKER, S. M. 1909. The causes of the Zoning of Brown Seaweeds on the Seashore. 
New Phytologist, vim, p. 196, and 1x, p. 54, 1910. 

BERTHOLD, G. 1883. Ueber die Verteilung der Algen im Golf v. Neapel, etc. Mitt. aus 
den zool. Stat. zu Neapel, 3, p. 393. 

CLEMENTS, F. E. 1905. Research Methods in Ecology. Lincoln, 1905. 

CoLtutins, F. S. 1905. Phycological Notes of Isaac Holden. Rhodora, 7, pp. 168-172, 
222-243. 

Corton, A.D. 1911. On the Growth of Ulva latissima in Excessive Quantity. Royal 
Comm. Sewage Disposal, Report 7, App. tv, p. 121. 

CowLes, H.C. 1899. The Ecological Relations of the Sand Dunes of Lake Michigan. 
Bot. Gaz., 27, p. 115. 
Darwin, G. 1910. Tides. Encyclopedia Brittanica, 11th edit., vol. xxv1, p. 940. 
Davis, B. M. 1913. Bull. Bureau of Fisheries, 31, 1911, Washington, D. C. 
Davis, C. A. 1910. Salt Marsh Formation near Boston and its Significance. Eco- 
nomic Geology, 5, p. 631. 

FARLOw, W. G. 1881. Marine Alge of New England. Report of U. S. Comm. Fish 
and Fisheries, 1879. 

FULLER, G. D. 1912. Evaporation and the Stratification of Vegetation. Bot Gaz., 54, 
p. 424. 

GRAVES, A. H. 1908. The Morphology of Ruppia maritima. Trans. Conn. Acad. Sc., 
14, p. 59. 

HARSHBERGER, J. W. 1909. The Vegetation of the Salt Marshes, etc., of Northern 
Coastal New Jersey. Proc. Acad. Nat. Sci. Phila., p. 373. 

1912. An Hydrometric investigation of the influence of Sea Water on the 
Distribution of Salt Marsh and Estuarine Plants. Proc. Amer. Phil. 
Soc., 50, p. 457. 

JOHNSON, D. W. 1913. Botanical Phomena and the Problem of Recent Coastal Sub- 

sidence. Bot. Gaz., 56, p. 449. 
KEARNEY, T. H. 1904. Are Plants of Sea Beaches and Dunes True Halophytes? Bot. 
Gaz., 37, p. 424. 
KJELLMAN, F. R. 1877. Ueber die Algenvegetation des Murmanschen Meeres an der 
Westktiste von Nowaja Semlja und Wajgatsch. Nova Acta Regie 
Societat. Scient. Upsaliensis, Volumen Extra Ordinem, 1877. 
1878. Ueber Algenregionen u. Algenformationen im Ostlichen Skager Rack. 
Bihang til Kongl. Vetensk. Ak. Hdl., 5, No. 6. 
Lewis, I. F. 1914. The Seasonal Life Cycle of some Red Alge at Woods Hole. Plant 
World, 17, p. 31. 

Letts, E. A., and E. H. RicHarps. 1911. On Green Seaweeds in relation to the Pol- 
lution of the Water in which they occur. Roy. Comm. Sewage Disposal, 
Report 7, App. 1, p. 72. 

LIVINGSTON, B. E. 1911. A Study of the Relation between Summer Evaporation 
Intensity and Centers of Plant Distribution. Plant World, 14, p. 205. 

1906. Carnegie Inst. Wash. Pub. 50. 

LORENZ, J. R. 1863. Physicalische Verhdltnisse und Verteilung d. Organismen im 

Quarnerischen Golfe. Vienna, 1863. 
OLIVER, F. W. 1912. The Shingle Beach as a Plant Habitat. New Phytol., 11, p. 73. 
OLTMANNS, F. 1905. Morphologie u. Biologie der Algen, vol. m1, Jena. 
OSTENFELD, C. H. 1908. On the Ecology and Distribution of the Grass Wrack (Zos- 
tera marina) in Danish Waters. Report of the Danish Biological Station 
to the Board of Agriculture, xvi, p. 1. 

TITTMAN, O. H. 1910. Tide Tables for the Year 1911. U.S. Coast and Geodetic Sur- 
vey, Washington, 1910. 

TRANSEAU, E. N. 1908. The Relation of Plant Societies to Evaporation. Bot. Gaz., 
45, p. 217. 

1913. The Vegetation of Cold Spring Harbor, Long Island. I. The Littoral 
Successions. Plant World, 16, p. 189. 

WARMING, E. 1906. Dansk Plantevaekst. 1 Strandvegetation. Copenhagen and 
Christiania. 

. 1909. Qicology of Plants. Oxford. 

Yapp, R.H. 1909. On Stratification in the Vegetation of a Marsh, and Its Relations 

to Evaporation and Temperature. Ann. of Bot., 23, p. 275. 

















162 


THE RELATION OF PLANTS TO 
TIDE-LEVELS 


A STUDY OF FACTORS AFFECTING THE 
DISTRIBUTION OF MARINE. PLANTS 


BY 
DUNCAN S. JOHNSON AND HARLAN H. YORK 





WASHINGTON, D. C. 
PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON 
1915 


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